Ah yes, been there, done that. Ex-wife was undiagnosed BPD. She remained undiagnosed because she was beyond manipulative (BPD trademark) and didn't exhibit the uncontrolled rage associated with the disorder (unless she thought she could do it without others observing it). She was very high functioning. I didn't realize that what she had until I asked for a divorce. Then, the BPD behavior just rushed out of her. From stating she would punish me for blowing off my commitment to joining a dating site 4 days after.
She was the world master at gaslighting. Before I found out what that was, I just called it a Colleen.
Gaslighting - Wikipedia, the free encyclopedia
Fortunately, she left me alone after I made my assertion that she had BPD. Like most borderline's she refused to admit she had it but my bringing it to light hit a bit close to home for her.
BTW, there are some really good message boards for those who have/had a loved one with BPD. I was on one for a short period and it was incredibly validating to read posts from others that could have been a narrative of my own experiences.