How to win ex gf back?

Ok this is kind of a long story so I'll try and sum it up. I left my gf of 3 years 8 months ago to pursue a career. I just broke it off and closed the book with her as I thought so strongly that I would never be back and didn't want the pain of a long distance relationship. So, as it turned out I ended up coming back and of course she was in the process of moving on with another guy and emotionally withdrew her heart from me. I was able to convince her to hold off to ingite what we once had and I postponed their getting together as long as I could....But to this day they have been going out for 4 months. lol She expresses all the time how there are so many things about him she doesn't like and that annoy her, however, he is in love with her and gives her a lot of support in her work. (she is a ballerina and so is he). She says she doesn't know if she loves him and keeps on going back and forth between us. She's cheated on him with me 3 times now....however, I think her feelings are somewhat tainted for him. We give eachother like 2 weeks- month worth of space and then always come back to eachother. Everytime we hook up she retracts and goes back to being emotionally shut off. (and its not the cuz the pion is on fire ;) Maybe this is damaging because she sees it as de-valuing our love into lust? Because in the end she she goes back to him. so idk....It seems like she wants us to work but is just scared to get hurt again especially because she already has security with the other guy....so I ask how to get her back? Will it take a lot longer than a month of ignoring her to make her miss me even more? Would it work to my favor to be friends and communicate with her?