Girl problem, please help!?

The problem is your talking to HER ex bestfriend. why? Shes mad at you because of that. Pretty plain to see as long as you keep talking to HER ex bestfriend youll never make up. Is her friend that important to you then your gf? If so then your with the wrong girl. You can have friends, but you cross the boundary when your friends with her ex besty. The stupid thing to tell her was you ran into her and talked while she was shopping for lingerie, you must be young and immature. You need to understand woman before doing such stupid things. Hopefully you can make up if its not too late for you. Good luck.