I was in a long-term relationship with a woman with bpd. Way too much to go into, but a lot of what you write is familiar. The biggest problem for some people with bpd is openness to the diagnosis. My partner was never, ever open to a serious discussion about it. She is talented and on the most superficial level, gifted interpersonally. Unbelievably charming. Ridiculous IQ. Also quite externally attractive. These things are what allow her to get by in the world. She operates at a level of zero emotional depth. Lots of challenges in the relationship, not least her spectacular cheating and dishonesty. Things finally crumbled and that was that. We barely speak now.

I knew what I was getting into. And I did it anyway. I thought we could get her into DBT and get her some skills and she might improve. I loved her. But she did not want that. And if there is one thing you can take to the bank about bpd people who are not in recovery, at least based on my experience, it is this: they almost always win.