How do i move on?

I am in love with a girl but im not gay and she isn't neither, we were together for 3 months and we were so in love but her ex boyfriend from 3 years came back into the picture and she started treating me so bad and then she went back to him and he treats her bad, i wnat her back but she says she doesnt want me back because she's not gay. she said she wont be able to ever get over me no matter how hard she tries because she loves me more than she loved him. what the hell do i do? i want to move on but my heart tells me not to let her go cuz she means it and shes just confused and to give her time she will come back but my stupid mind is sayin 2 let her go she treats me just like her ex is treating her and she is playin games with both of us by kissin up on me while she's back with him again. =[