Hello, I am an 18 year old male, I've been really struggling to cope with the events of a dangerous relationship. My ex-girlfriend is an 18 year old female with BPD (She hadn't informed me until later in the relationship). I would like to maybe gain some understanding and insight onto why she acted the way she did, so I can figure out how to feel and move on. 
We had a very toxic relationship, she would constantly pick fights, cry, or yell at me about me leaving, other girls she was nervous about,  how she couldn't be intimate with me, etc. I always sat and was patient with her, and we would always resolve these arguments. Only for her to start the exact same argument the next day. We were on and off too. During a phase where we were together we decided to finally have sex for the first time. She insisted that she was on birth control and that we do it raw. Me being a horny idiot said ok. So we did. And I finished in her. I asked her the next morning if she took a plan b. She said yes. Only for her to come to me in the hallways at school two days later crying and telling me that she didn't. I stuck around for this because it was terrifying for the both of us. I blamed myself. I gave her money to buy a plan b, and asked that she send a video of her taking it. She refused to send a video. Somehow she miraculously ended up getting her period. I was upset with her. But I still stuck around because I loved her to death. Fast forward a couple weeks and she's upset that I didn't let her keep the child after we both agreed that we weren't capable of being parents, and that we didn't want children. (She would always ask for a baby, but she would say she didn't want a kid, she wanted a baby more as a pet). 
A month later we're still together and I found out that she had been telling people that I had physically abused her ( I never did, I have suffered abuse and take it INCREDIBLY seriously). This broke my heart and I decided to confront her about it. I told her that I didn't understand why she would do something like that when we were starting to do so well. This would be the last time I would talk to her in person. We decided to split up after coming to a resolution.
I soon decided to start a new relationship with a girl who saved my life. Only to find out that my ex had found out and started stalking her and had her friends stalk her too. She called me cursing me out, and crying. There was nothing I could do. I was scared of her. So I blocked her on everything. I find out very soon after that she then started telling people that I had sexually harassed and assaulted her (never happened, I have proof. this hurt me so much I started hurting myself). 
She makes these claims and places herself everywhere that I am. She continues to say things to this day. I see her everyday because we go to school together. 
I still feel emotionally attached to her. But I also despise her. How does one go about feeling about her. Should I try to be understanding? I would like to gain some perspective on her condition so I can figure things out.