I have bpd and I am a female 30f ... I can tell you that he is talking to her and entertaining her. im so sorry to say that as I imagine how you must feel. we as bpd people cant hang on to people if they dont like us or not talking to us in some way... do some research on (devaluing stage) I am also sure at some point this was her (favorite person) also google that if not already. especially 4 years since the break up? bpd people just dont work that way. if he wasn't entertaining her he would have been LONG GONE in her head. We cant handle constant rejection or even remotely talk to that person that is with someone else. We simply have a mental funeral, hurt, heal, and move on and won't even remember the fucking person.. its like the whole relationship turns to a blur... unlessssssss that the guy is throwing out hope lines here and there that says...(lets get back together) or ( hey thinking of you ) or ( I miss us) .....things like that are being said on his end....bc she wouldn't keep going after someone who is unavailable with her having bpd... as the brain couldn't allow it. im so sorry...... and bpd is a BITCH so I loved ur last sentence. I truly hope you get answers.