I need advice on how to get over this girl?

I was madly in love with this girl, who i was in a rebound relationship with, This girl was my first real girlfriend who i seriously wanted a future with, we were together for one month and she started to fall back in love wih her ex, She left me to go back with her ex and now the pain and heartbreak i feel is tremendous i keep telling myself she will come back because she always fights with her ex. I feel as if falling in love again is impossible, I feel so betrayed. I've decided to move on but the hurt and the feelings i have left for this girl still remain. How can i fix my broken heart and get over this?