This might be a little rambling but please bear with me. 
GF was recently diagnosed with BPD after a nasty episode when i asked her to move out and I've been reading up on the condition and now i'm starting to worry that our entire relationship has been her manipulating me.
A little background.
We met about 2.5yrs back through mutual friends and she says she felt something immediately. I wasnt all that enamored but we ended up hanging out when she invited me to the birthday of a friend of hers a few weeks lakter.  Here's where i really should have started paying attention. At that event were her friends and an older man, let's call him M. When i got there, she was sitting next to M and introduced us. I spent alot of time talking to the birthday boy and she only really started intetacting with me when M left. After he was gone, we got to talking. I was going out with friends later that night amd she came along and ended up at my place, where she made a move. Honestly, at the time i wasnt really looking to get into anything since I'd come off a bad breakup a couple of weeks earlier and wasnt in a great headspace so i turned her down. Anyway, she stayed, i made her breakfast the following day and we watched tv all afternoon. She still wanted physical contact though to the point where she asked to me to 'just hold me' which i did. After that we hung out alot more and she'd call all the time so we got comfortable with each other and started sharing things about our pasts, though she always had this fear that telling me anything sensitive would come back to bite her because, in her words "people leave and they take your secrets and insecurities with them and use them against you'. I have trouble trusting people too so i could understand why she felt that way so we made a pact. Honesty no matter what. No matter how painful of how insecure we felt about something, we'd always share. At this point i told her that what i really needed in my life was a good friend and it was very easy talking to her so our relationship shouldnt veer romantic. She was adamant that she couldnt be just a friend even though i told her that i dont see myself getting married or having kids. Its just never been part of my plan. Thats when i found out that she'd been in contact with an older friend of her brother's and he'd proposed to her recently and she said no. I didnt think much of it at the time. Anyway, a month after we first hung out, she says she loves me. At this point we still havent had sex and though we had gotten pretty close emotionally, i found it odd but again brushed it off. We keep hanging out for another month or so before we get physically intimate.
At this point, i have a clearer piccture of her life, which seems to revolve around two social circles. One group of social girlfriends and her work circle which sometimes hangs out with M. This is one of the bits that worries me now in hindsight see. I didnt meet her work friend circle ( which includes her best friend) untill an incident occured.
One evening, after a bad work review from her boss, she goes out to drink with her work buddies and asks me to go pick her up. This is about 5 months into the relationship and its the first time i'm meeting the girl who i later find out is her best friend. On our way home that night,  I ask her what happened and she goes through it. Her boss wants to see her put in more effort at work. He thinks she's better than alot of the people she works with,  but isn't pushing herself hard enough. I can see how this makes sense and I told her that though she may disagree with him on this and maybe she is doing enough,  he did ask for a few specific things she could do that didn't seem like too much to ask (like stay after hours once in a while... Seemed like pretty benign stuff to me). She totally lost it here and started talking about how I was taking his side and I didn't really care about her. She starts talking about how if she loses her job, I need to support her and I quite simply said no.  We'd only known each other for a few months and I wasn't going to do that.  At this point she gets physical.  Pushing me around, slaps etc. Until she tires herself out and falls asleep. The following day, I leave early for work and she stays in my house (unknown to me) drinking. When I get home,  she picks up where she left off and escalates.  I tell her I'm not going to stand for this and she should leave and things get really out of control.  At this point she threatens to jump off my balcony and kill herself.  I stop her from going out there and she runs to the kitchen and grabs a knife which I have to wrestle out of her hands so she runs to get another one....  you get the idea.  This goes on till she tires herself out again and falls asleep. The following day she starts getting into it again and I tell her she leaves or I do after relating the previous night's events to her (she claims to have memory lapses when drunk) . She eventually leaves but spends the next three days calling me to apologise. I only agree to meet with her on the condition that she sees a professional first. I never could verify of she did,  but she's says she had a session with a psychiatrist and we talk and she promised it would never happen again.... I foolishly take her back.  
Now that I understand BPD better, I can see how me not validating her feelings at the time would have made her feel rejected. But here's what I don't get. This was coming from her boss,  not any sort of father figure (they're almost of an age) or romantic attachement, so why would negative comments from him send her into that spiral? My paranoia tells me that it's because she we involved with him at the time, so any criticism from him would have been filtered as rejection and me siding with him in any fashion would enhance the feeling. Am I out of line here? 
A little more context about her and her boss:
After that incident, their work relationship seemed to have soured alot. He basically tried to fire her and ended up putting her on probation for almost a year.  Then oddly enough,  as soon as he got married,  everything went back to normal. His wife works in the same office and I even joked to the GF that all her work problems probably stemmed from the wife's insecurities about her relationship with him. 

And then:
Things sort of went back to normal between us and she seemed balanced for a while so I didn't insist on her actually being in therapy since I knew she couldn't afford it. We had occasional fights but nothing that escalated to the point were things got physical.  The one curious thing was the fact that she kept insisting that the two of us hang out with M because 'He's my friend and he wants to get to know this man who's made me so happy'. I found the whole situation abut odd but I relented. We work in the same industry and he was an okay guy I guess. About 6 months after we'd started hanging out, she needed to go into minor surgery and had to be hospitalized overnight and I went with her and stayed overnight to make sure she was okay.  I think the context is important for what happened next.  While she's recuperating, she's staying with me and I keep pushing her to look for a new job because at this time her boss has her on probation and she's unhappy at work.  One day, towards the end of her recovery,  she leaves her email open and I take a peek. I search her mail history for the nickname she gave me,  and emails from a few years back pop up.  Emails to M using the same nickname she'd given me (M, BTW is and was married). And alot of things about the two of them suddenly added up.  She was still recovering at the time so I didn't bring it up,  but a few days later i asked her to her face of there ever was anything between the two of them and she acted really shocked and denied it. If I hadn't seen the proof for myself, I'd have believed her. She comes clean only after I say that I saw the emails, gets very angry with me for invading her privacy,  which I fair enough,  and refuses to talk about it and gets violent. At this stage I tell her that I don't think it's over between them and ask her to take off the only piece of jewelry I've never seen her without (an anklet he'd given her for her birthday). Once again I asked her to leave and tell her we're done (Honesty about everything was the number one rule) and she gets very violent and refuses to leave.  I head off to work that day and she's calling me all day talking about how I never cared for her (I'd just spent 10days off work looking after her so this one really baffled me) and that she'd kill herself. Even sent me a picture of the pills she was going to take,  at which point I called emergency services.  When the ambulance got there she told them she was fine and they left.  Needless to say I, got a ton of grief for even calling them. A few days later she wants to talk about M and insists that the only reason she didn't say anything was that the two of them were only friends now and she was ashamed of the relationship.  Plus it was her past and therefore none of my business. It didn't add up because she'd told me about a sexual relationship with her uncle (this happened when she was an adult, about 24) and I had I known she'd even spent time with M's kids after they 'broke up' (His wife lives in another city and the kids visit him often)  I don't understand how she could feel ashamed about screwing their father and hang out with them at the same time. And based in their emails,  it seemed clear to me that she'd wanted more and he'd stopped that because he was sleeping around.  She even called him out on it. Again,  I can see how she could need the sort of validation a married man could give her.  But, my paranoia here says they were still intimate when I met her. She denies this vociferously but I can't shake the feeling, especially after I found the anklet in a box next to her nightstand 6months ago.  I think she finally got rid of it that night. 
Ever since then,  our relationship hasn't been the same. I tried to talk about the M situation and get past it but till I found the anklet, everytime I brought it up,  she'd say that I was using her past against her and that's why she shouldn't open up to people. Things came to a head when I found that anklet and she finally talked about their relationship. With an understanding of BPD,  I see now that he acted as a father figure and was actually a positive influence on her for a while,  I just don't think she's being truthful about when things ended or how she really felt about him. 
You might ask why I'm still with her even though i clearly don't trust her.  Earlier this year,  things seemed to be going well. As much as I have my doubts, the M situation is behind us and as far as Im aware they haven't been in contact since I first confronted her about him.  I was worried about one of her workmates and her but he's left the country and we settled into a rhythm.  She's somewhat secretive (deleting what's up messages every few days and so on)  but I forced myself to look past it. I never wanted to be the jealous, controlling type. I've never been in a relationship that lasted more than 6 months, and after being with her for so long and being in stasis,  I guess I felt the need to do something to move things forward. She had an abortion earlier this year beacuse I don't want children and from her viewpoint,  she felt that she had to choose between me and a baby.  I told her that I'd support her whatever she chose and I have the means to support her fiscally if she chose to keep the baby but I don't see myself being a good parent so I wouldn't want contact with the child and I think that may have left her feeling like she was painted into a corner. I have always tried to be upfront about this and we discussed the probability when we first met,  but going through it is something different. After the abortion I suppose I felt that I needed to reward her somehow?  ( I'm not sure if that makes sense)  I guess in my head she actually really chose me here, so I asked her to move in. About a month after we moved in together, she went for a work friend's wedding and got drunk, in spite of the fact that I have asked her more than once to limit her alcohol intake and avoid getting drunk since she loses control when inebriated. She came home that night and got very aggressive with me. Our argument was essentially about why she's not good enough for me to marry her. Things got thrown, things got broken, I lost my cool and slapped her and I'm not proud of it.   The following morning she tried to pick up where she left off and I asked her to leave before I left for work. After weeks of silent treatment and arguments she finally did move out but went out and got her friends involved and they interceded on her behalf.  Stupidly, no broke down and allowed her back in the house,  on the condition that we sleep in separate rooms.  She wasn't having any of that and kept creeping into my bed at night. Unfortunately I broke down and we had sex once. After that I tried to put my foot down and told her she could only stay if she actually slept in a  separate room and there was going to be no physical intimacy between us. I even suggested that she move out and I cover her expenses for a few months because I was done with the rollercoaster and wanted to see other people. She left that morning but came back at night drunk. She got physical with me and I just walked out to go cool off.  When I came back to the house a few hours later,  everything was destroyed.  Clothes, electronics,  curtains had been ripped with a knife... I got whatever I could together and tried to leave but she sat herself in my car and refused to get out.  I still had a little control at this stage so I got in and drove. I just wanted to find a place to sleep for the night.  Where I really lost it was when she pulled the handbrake while I was driving about 80mph on the highway.  I've never wanted to hurt anyone before but at that point rage took over and I attacked her. I wanted her to feel pain,  alot of it and I could barely stop myself after punching her a few times. I resolved at that point that keeping some distance was the only thing I could do,  drove to an abandonded lot,  got of the car and grabbed a taxi to the hotel and left her there. 

The following morning, her bestfriend calls me and tells me she got a distraught call from the gf asking her (best friend) to call her parents and apologise for what she was going to do.  Now I know that BPd sufferes typically mean suicide when they say it and it's not normally a manipulative tool,  but she knew the first person her bf would call was me. I refused to engage and asked the bf to let her calm herself down but she didn't listen to me and ended up taking her to see a therapist.  Fast forward a couple of weeks and gf has been diagnosed and is in therapy. I'm glad she's finally getting help and I want to be supportive but I also want out.  She's insisted that we try couples therapy but I know I'm not happy here and I can't keep doing this but short of packing up and leaving, I don't know what to do. I can't really do that because she needs help paying for therapy and relies on me for support.  She knows that sleeping in the same house as her now scares me and I've told her that I worry that we'll fight and she'll lose control and stab me in my sleep but she doesn't care.  I worry that abruptly leaving will just pull the rug out from under her feet and destroy whatever progress she's making,  but that's what I'm about to do.  Move out and cut contact.  I still think she lied to me about M and probably cheated with her work colleague as well but of course she denies all this.  Am I being paranoid about this? Too harsh on her maybe? 

