Most Helpful Girl
Then dump this girl. You obviously don't love her. Go talk to your ex girlfriend. Tell her how you made a mistake and see if you can work things out.
Sometimes the grass isn't greener on the other side. She might be pretty and cute, but after being with her, you can see that she is just drama.
We all make mistakes, and this is one of the mistakes you are going to have to come to terms with.