Well, I will share my story. Mine was with a preacher's wife. She had 4 kids by 4 different guys. She said the guy abused her and cheated on her. I had seen the brusies he inflicted on her and witnessed the guy's rage. I guess the fact he cheated on her and beat her made me feel better about the affair. However, it's not something I am proud of.
Anyway, this lady told me that no matter how things ended she still hoped we could be friends and that she couldn't imagine not having me in her life. I don't think she was BPD. The thing that made her hard to resist was the fact that she treated me in the way I'd ve expected a girlfriend or wife to do. She cooked for me, did my laundry and even ironed the clothes, paid for my rental car, came to my apartment on my birthday when I wasn't there and put up a balloon and cake, came to my soccer games. She asked me not to fall in love with her (which was ok with me at the time) and then later she started to confess her love for me etc. I fell in love with her too.
Few months later she said he husband confessed about his affair to her and she felt obliged to confess to him too. She had initially promised me that she wouldn't mention my name. Even if she was going to mention my name I would've understood but she gave me that false sense of security; only to later go and mention my name to her husband. She even went as far saying that the few months between us never happened and then she got cold ( I felt betrayed). Then her husband started calling my work and home and making threats. I had to get a restraining order against him. He even trailed a friend of mine who was driving my car (because he thought I was the one driving) and then interrogated him. Eventually things kind of diffused. She got a divorce from him and although I've run into him in public places. He just says what's up and that's it. Well, things could've been worse. So, MrBatman. I hope you can learn something from my experience. I'd say this was one of the craziest things I had ever done. In the beginning it was fun and adventurous but the end was sour.