You already know this deep down, but I will say it anyway -- you cannot change the way someone feels. *Sometimes the heart has reasons that reason does not understand.* Although what she has done doesnt make sense to you and it sucks beyond belief for you, she too cannot help how she feels no matter how much it hurts you. Chances are she had been thinking about breaking up for awhile and finally got the nerve to do it -- but it was sudden to you. She should have talked to you if something was bothering her. There's nothing you can do about that now, or even then. It was up to her. SHe may even have been interested in someone else -- perhaps this other guy she was hanging out with a few days later. And if so, then fine, she's not worth your time or pain! You don't want to be with someone anyway who doesn't want to be with you or whose heart isnt completely with you. You deserve better than that, and you will have it one day! Best wishes