This is an old thread now, but I did. Or at least I think I did, as she didn't have a formal diagnosis.
Basically, I knew her through running and she was very attractive but never seemed to have a boyfriend (more on that later). Seemed to like me and was very flirty with me but at other times would ignore me. I gave her a ride in my car to a race once and once we were there, she completely ignored me and I had to search for her to check whether she wanted a ride back (she didn't). Secretive. Inconsistent. Hystrionic and loved drama. Flirty yet pretended to be shy. Got jealous almost to the point of stalking (turning up where she knew I'd be in order to visibly ignore me if she saw me talking to another girl). Turned out she had a long term, long distance boyfriend that she kept secret. Stupidly, I ended up having a short relationship with her, which ended with her ending it abruptly. I much later found out she'd ended it because she started seeing one of my best friends (who cut me off and I couldn't understand why at the time). Later, he told me the reason and she ended up ending it with him after a few weeks for someone else.
A couple of years later, stupidly I got together again but by this time I had moved out of town and it was long distance. So I was only seeing her once a month or something but staying over all weekend and things were great. Best relationship I ever had or so I thought until she ended it abruptly again, over the telephone "Sorry but I'm seeing someone else now". She did admit to cheating with a particular person however. She refused to speak any more or meet up and I've never had contact with her since. It became clear at that point she had lied numerous times about matters so important that I would never have agreed to a relationship of any kind with her if she had told the truth.
Since it was also the second time she had pulled the trick of the devastating end of the relationship, I am convinced she enjoyed the drama and deliberately manipulated it that way so as to get maximum "reward". I "think" she had convinced herself that she was a nice person by ending it and not cheating any longer and she is very concerned about her image and controlling it to the point of paranoia. She also by this time had a notable history of not holding down a job, getting other people to give her money (although not me, perhaps I was next in line), taking up and then giving up numerous sports and hobbies (she is onto a completely different sport than running now) and dropping friends. At the moment, she is hanging around a lot of elderly folks and socialising with them which is kind of weird as shes in her early forties and they are all in their late sixth and seventh decades, and older.
Later found out from a mutual friend that she got married quite quickly after ending it with me but to a completely different guy from the one she cheated on me with (undoubtedly she was cheating on us both at the same time). Her spouse is much, much older than her and not a very attractive guy, not her type you would have thought.
My pyschologist friend obviously avoided cod diagnosis but did suggest she was borderline but also had elements of multiple personality disorder (disassociative) and avoidant and was quite machiavellian (calculating too). Its as if all of us who knew her knew and could accurately describe a completely different person, with different interests, and even different voice and clothes. Very harmful to be around and I suspect she would like to reel me back in for a bit of cheating if she could (I won't explain why, it doesn't make sense unless you know how calculating and manipulative she can be) as she appears to be keeping her elderly spouse off all her social media photos and trying to pretend to be single.
Terrible person and a lot of my interest in her was actually in trying to work out the "mystery" of who she really was. Now that I know, and now thats she getting older and beginning to look like who she really is, I don't find her remotely attractive any longer and am glad to have got out intact.
The lesson to be learned is that I would be able to easily identify with and avoid another person like this again. In fact, I always had my doubts about her and as I said earlier, it was more about solving a mystery for most of it, looking back. I'm happily together with a kind supportive partner now and look back on her with something between disgust and pity. Pity because she was a person with a lot of potential who had a lot of advantages in life and she isn't doing well. I'd never have contact with her again, she is so poisonous.
BPD quite often doesn't present on its own and I suspect my ex was also a sociopath with some other disorders too. I would have said it was completely untreatable.