Sounds a bit familiar.  My college boytoy was NOT a charmer, and did not understand "fidelity".  Anywhoo, I heard a friend of mine tried to get in his pants--and I dont know if she was successful.  But once she found out I knew--it was like she suddenly needed my approval.  It is not like I yelled at her or anything.  The man was a manho, so...who to be angry at but myself, for putting up with him?
"what's wrong?", "are you mad at me for something?","why dont we hang out anymore?","Is this about that thing with XXX?"  The girl would not let up.
Long story short, she was doing this at a party,  I embarassed her in front of our entire group of friends, said some choice phrases, apolgized to the group, and left.  Apparently, she had made passes at everyone ELSE'S boyfriends at one time or another.  So, after I left, all the OTHER women there saw her weakened state, and took the opporotunity to confront her about the "incidents".
I felt bad for yelling at her publicly, but I guess it needed to be said. (?)