I've been back and forth with my expwBPD, after an initial period of great and what seemed healthy to suddenly dealing with her desire to be friends with her ex who she had previously said was toxic. Her insistence, and the conflicting feelings, created a

to me. She swore they hadn't been in contact. Eventually, I said that as long as she was honest about it, I'd eventually be cool with it, but I wasn't ready yet, and appreciated it if she could, in the mean time, process this/any unresolved feelings with her therapist. She agreed. I thought the matter was closed.
Eventually I found out that after a fight, she met up with the ex behind my back, and when I outright asked initially, she lied. She said it was a good meeting that let her know there were no romantic feelings and that they could be friendly down the line. She then said she felt that talking about this to the therapist was good for now.
The therapist agrees that space from the ex is good, and says that toxic people always remain toxic and advises her not to have contact. She tells me this and agrees with the therapists. Two weeks later, she's drunk and pushes the issue again. I tell her I'm not comfortable yet, and am open to it, but am getting past the shady behavior and broken promise already around the ex. I said that I want the trust to be restored a bit first. The next say she starts to go on about the ex's redeeming qualities. I'm now very uncomfortable and say I don't like this boundary pushing and changing, and don't want to be in a relationship with active threats that even the therapist says isn't great, so I gave her an ultimatium and she chose not to choose, which of course is a passive choice so I broke things off.
Recently, she came back to me, months later, and explained she'd been in a rough place in her life, got a job finally after being unemployed for a year, had fixed strains with her family, and felt she's just sabotaged things. She mentioned too that she'd seen the ex about 2 months back and that they were friendly now. (She had casual hookups with others during this time.) I said that we could talk about moving forward but only once space was taken with that ex. She agreed, and eventually admitted that they'd slept together then and stopped to be friends. She said she's send an email taking space, and then she started to negotiate on whether it was an email or phone call. I tried to stick to my boundaries and not fight, just saying "I'm only comfortable with an email and no contact for now". She agreed, sent the email, and then the ex replied about 5 times within 6 hours, telling her how mean this was, saying she should've called, how aggressive and mean this all was, and essentially asking to be emotionally taken care of (the email was actually pretty nice--no need for it not to be).
Of course, she then wanted to console the ex by calling her. I was really upset, and talked about how that made me feel but also how manipulative this was of the ex, and asked "do you think that if you'd have called that any thing would be different?" She said no, put it to rest, until the next day when she said she felt bad and was going to call the ex and emailed ex to say so. I said I accepted her decision, but that since it crossed my boundaries again, I was no longer going to be talking to her and there was no chance for us to communicate in the future, and then wished her well. She was angry, part cold, part pleading, also said I was being controlling, but I told her it was done for me and that I was blocking communication so that I could move on. I finally found the self-worth I'd lost in the confusing mixed messages before.
On the one hand, I just COULD NOT BELIEVE that she was repeating history and keeping the triangulation drama alive. On the other, OF COURSE she was!, and seeing this was a gift letting me know that had I stayed before, nothing would've changed really.
The weirdest part is that when we recycled this time, I was aware of her PD, and of the fact that it likely wouldn't work, and couldn't even give me what I want. I wasn't even fully into it, so I can't really say why I entertained this drama at all. Anyone relate?