Sorry to hear this. Dont bother yourself with what she see in the other guy that she dont see in you. Its plain and simply a matter of chemistry, shes not physically attracted and its not something you can change. You are obviously a better person then the other guy, he beated you with a group...
She may become attracted to you later on. Though, the way you describe the situation, I would suggest to stop seeing her immediately and completely. You should be fine in a matter of weeks ; ).