I need some input onto how to handle a situation. I have a cousin (Frank)of mine who happens to be fixated on this girl (Mickey). It all started when I had a party at my house last summer. After they had been friendly for awhile,she told him that she had broke up with her boyfriend cause she was tired of how jealous he was at my cousin and that she had feelings for him. So my cousin decided that he was gonna ask her out but he was gonna give her a couple of weeks so she can get over her breakup.She was also known to sleep around behind her boyfriends back even though my cousin didn't know about it. But when he was getting ready to ask her out,she just started acting cold towards him and just kind of disappeared for awhile. But when she finally came around again she told him that she got back with her boyfriend and she was no longer able to hang out with him. But a few months ago she told everyone that she broke up with her boyfriend again and this time it was for good. But she still is acting cold towards him but last week she called him asking for help because she was moving to a new apartment. My cousin decided to help her out anyways and when he went to her apartment to help her move,he found out that she got back with her boyfriend again. What's messed up is that this girl happens to be best friends with my fiance and I definately don't want mess things up with her. So how should I go about telling my cousin that he should stop trying to be friends with this girl? And how should I go about telling my fiance on how her best friend really is?