She is acting crazy and I don't know why or what?

[Got I]

My GF and I are both in college and we left for summer on may 7th.we had been dating very strong for 7 months and planned to spend our lives together..i was going home and she was going to new york for an internship.We dated till june 2 and there were some small fights over the phone until that time.After we broke up we still talked everyday multiple times per day but as late june rolled around she starting getting angry and said she no longer wanted to talk and kept yelling at me etc and said she never wanted to talk to me again, hated me, and we would never get back together.At that point I started to see another girl and we kissed a few times and when she found out she went crazy, started crying and said she never meant anything she said and now we can never get back together.She is blaming me for all of this and refuses to talk to me again and said some guy at work asked her out and she is considering going out with him. I'm not sure whats up any ideas on why she did/is doing this?