I would like to make it illegal for anyone to say they have "graduated" from this board because all it does is jinx us. Sorry to hear the news Kaw. What to do? IGNORE IT. It is still all about you and your actions. You can't stop the "fantasy", all you can do is join it. The alternative is to ask "are you contacting him?". The answer will be no and then you will be angry because she is betraying you and lying to you. Oh yeah, and then she knows that you snooped. I have been there and you don't want any part of it. All I really can be sure of is what not to do.
You are in a really tough spot but at least he isn't contacting her. It will take time to convinve her through your actions and behavior that you are the one. Settle in for a long battle and pace yourself. Don't let her get you too low or too high. I screw this up all the time. Human nature is to want what we can't have. That is affecting both of you right now. It sounds like a physical attraction thing for her so I guess my only thought is work on that. That is something that helped me "keep her home".
Hey , if I hear you are snooping anymore I will have to come over and rough you up. It is torture that you do not need and will take you further away from your goal. I promise. I have been there myself.