*I made this post in some advice subreddits but maybe this is the best sub to get some help and perspective. 
My girlfriend is diagnosed with BPD and went to therapy for many years. 

I'm going to paste the post now:*

CONTEXT: My ex and I dated for 6 years. We broke up 2.5 years ago. I started dating my current girlfriend 6 months later, so we've been together for 2 years now.

My ex girlfriend has now been becoming a big name in the music industry in my (small) country. Enough that her music is on popular Spotify playlists, TV and clubs from here.

I was with her for the beginning and part of the take off of her career, so I know a lot about her process in song writing and making of music. We ended in good terms, so we still talk sometimes and I still help her with her music when she asks. She doesn't ask for help often, but she asks sometimes.

I've made it clear to my girlfriend that I love only her and I'm not interested in having anything romantic with my ex again. We broke up for a reason. I still care about her a lot, though (I've known her for 14 years). She's my friend. She's very important to me.

My girlfriend understood that and was okay with it. I could notice some annoyance at first, but eventually she realised my ex is a friend and we're just platonic.

However, she asked me not to tell her about the stuff my ex and I talked about. I thought being fully transparent would help avoid jealousy, so I'd talk with my ex on speaker and include my girlfriend when I could or I'd tell my girlfriend what we talked about after. My girlfriend asked me to stop, that she'd rather not hear much about it unless it was something very good or very bad.

NOW: My ex has been working on a new album. It's about her life and stages in her life. One song is about her and me (as friends) and another song is about our past romantic relationship. She asked me for suggestions and eventually for my approval. I gave it.

I didn't tell my girlfriend anything. She's written so many songs about me and us. It didn't feel important.

A week ago, my ex sent me a file with the songs. The songs are great. I was visibly excited and happy. I listened to them on headphones for a while. My girlfriend noticed my excitement, asked me what I was listening to and I told her it was two songs from my ex's new album.

My girlfriend doesn't listen to her, but she tried to match my enthusiasm and give them a listen.

One of the songs has a line about a good night we had and a comment about how after 6 years of dating it only took me 6 months to find some other girl.

Needless to say, my girlfriend didn't enjoy the songs. She insisted it was fine, that she understood it's just a song and art and business. I fell asleep and apparently she spent that whole night finding and watching my ex's old youtube videos where she sang old songs she wrote about me while we were dating.

I woke up in the morning to her crying, asking me for an explanation. She is convinced we're still in love with each other, that I've been using her as a distraction while she is busy getting famous, that we'll get back together.

My girlfriend was genuinely hurt, heartbroken. She left my house and has been staying with her parents since then.

That wasn't our first fight, but it was the only where I saw her so afraid and emotional.

It's been a week now. She doesn't respond to my calls or messages.

She has BPD so I know fear of abandonment is huge and black and white thinking is what she does, so I truly understand the reaction. But I love her and I don't know how to help her. I want her to come back, but I don't want to show up at her parents house and force her to see me if she doesn't want to. She's an adult and I respect her choice but she's so wrong and God I miss her and I don't know what to do.

My ex offered to talk with her along with her boyfriend and explain the situation but I haven't told her about that yet since she doesn't reply to anything and I don't know if that would help anyway.

I guess I would like if someone could give me some advice? Should I be quiet and wait for her to come back? But she feels betrayed, so what if she never comes back? Should I talk with her parents? Should I end contact with my ex? I've already apologized for everything I could. She's very mature all the time but she has this panic of people leaving her that she's been working on for many years and I can't help but think I truly fucked up.

Help?

TLDR: my ex girlfriend wrote new songs about our relationship, I knew the songs were coming, but I didn't tell my girlfriend about it. My girlfriend heard them and she thinks my ex and I are still in love with each other. She left and has been ignoring me for a week.