I just wanted to clarify what I said; my suggestion would be to ask HER to talk to him about you as you seem to be in deeper than casual sexy time together... she seems to be wanting a relationship with you if she is trying to get you jealous. If you don't want a relationship and it was just fucking to you, then I think it best to tell her that and move on no? Otherwise sitting down with her, finding out what she wants and then going to him with it all would be my suggestion.... sorry, perhaps I wasn't clear enough before, so I'm hoping a recap will help some how.
Basically there are three options. As I said before; say good bye, say good bye and suggest she talk to her man about how she could get connected to her casual fucks and the last being to work on a relationship that is above ground.