Just to be straight with you, how do you know she hasnt banged the guy a couple of times allready? Usually the long phone talks and all that comes after. A woman in a relatonship should not have GUYS as friends on the side, its different if the guy was both of your friends. Its nothing to do with the other guy, its not his fault. Most woman like that will tell the guy how negleted or abused they are and totally put you down to make him think your an a**hole, so he wont feel bad doing what hes doing. Its all about her. Get out while your young and unmarried. Good Luck. Ive been there.