How to move on?

So I was in a relationship with a girl from august to october and she was making it as if I wanted to break up by making me think I want to date other guys that go to my school (we are long distance) and I believed her and we broke up, but we decided to be friends. A hour later she told me how she found someone else and how beautiful she was and sent me this girl's nudes almost to try to get me jealous. She was my best friend and now we barely talk and I feel replaced. As I think about the situation I realize that she mightve been cheating on me because how could she be madly in love with someone, be in a serious relationship, and then got nudes from her in a whole hour? Now I dont know what to do. How can I move on because now all I feel is that I can easily be replaced and just upset. I cant imagine myself with anyone else and now that home coming is coming up and she was planning to go from Florida to NY just to go to home coming with me and now I dont have a date nor the motivation to find one. Help!