What do you do if you got in an argument with your girlfriend and you don't talk to each other and she is hanging out with her ex instead of talking to you and fixing things?

It depends on what you were arguing about. If you cheated on her (not blaming you here) then you broke a major vow most of us would like to keep and hope to get from our partner (girlfriend, boyfriend, hubby or wife.) If it was something else and not all that serious then it sounds like you need to look for a mature woman in your life (meaning a girl your own age, but thinks along the lines you do) and you have the right attitude of trying to communicate and working things out. If you didn't cheat on her, and the problem isn't all that serious to begin with then she could have used this as an excuse to break-up with you and move on. Perhaps she has always wanted to be with her ex. This happens more than you think. People get ticked off at their ex, they want to be loved and cared for and find someone else and they truly are happy for a bit, but then reality sets in and they want their ex back. I feel this is probably what has happened in your case. I'm obviously not you, but the best thing to do is move on and take time out and go out with your buddies, then think of having another relationship. There are so many great women out there. Never settle for less than you give! Good luck Marcy