Can't get over cheating/!?

Okay... I'm sorta in the same situation here, I see where you're coming from. But there's a few things, first, you never stated if either of you are or were in love. Second, if this girl truly loved you, she wouldn't have cheated on you, despite the paranoia. To justify the means, my girlfriend sort of cheated on me about a week or so ago, but not with a guy. Although she did admit to it and that it was with twin girls, and I know most guys wouldn't mind that at all, but we've gotten pretty serious. Sorry about getting real specific, but on to the rest... Since then, I've been suspicious and asking things just like your situation, I mean, it's hard to trust if the girl IS flirty and most of her friends consist of only guys, right? And, honestly, the paranoia originally started from a previous relationship, and just hasn't stopped. So, I mean if you love this girl and she feels the same way, then talk with her. Get to know her friends better, find out what type of people she's talking to, but without being too controlling or intrusive. If you can't past what she's done to you, then my best advice is to break it off with her, get over her. Even if that means being single for a while. Just DO NOT start a new relationship uming that the girl is going to break your heart, because their philosophy is, "If they really think that, why not make it true?".