It doesn't seem like you could have done anything to warrant a closure free ending such as this. Truly difficult to say if any form of MI created such a scenario, not that coming to an understanding of borderline behavior doesn't help. Even if she is, underneath it all, she's still a woman bouncing around from one relationship to the next, these are her choices and her place to accept accountability for how hurtful her actions are. Could be some underlying dependency issues. Seeing 50/50 custody the way she did is black and white thinking.
I do find labeling can become a slippery slope, just because it could place one in a victim mindset. My exh is bpd and bipolar, it is what it is.