Very confused, I need some advice please!!!!!!!!

I just broke up with this girl that I have been seeing for 6 months, when we got together, it was like love at first sight, she had just broke up with her ex-boyfriend of 3years, and I had just left a 5 months relationship. Everything was going great and a few months later, like 2, her ex tried to get back with her. He called her constantly, came to her job and all that; he even went as far as talking to her parents. Through all this she always said that she loved me and that she just didn’t know how to get rid of this dude, she even said that she never thought that she would love anyone else. Things were great, I mean I was there for her, did everything for her, but somehow, she just wasn’t giving me all her love. We broke up a few times, because, she said that she was very confused and that she just couldn’t concentrate on our relationship, this never lasted, we always got back together. Two months ago, she finally decided to break it off completely with her ex, telling him that it was over and that they wouldn’t get back together. Everything was cool until, she talked to him on the net and found out that he was seeing this other girl and that he was bragging about how he was gonna sleep with this new chick, posting everything on the net, she called me crying and I was cool with it like I understand, and she told me that it was the last time she would cry because of him. We moved on but 2 weeks ago we got into a stupid fight and we didn’t talk for a day, I wrote her an e-mail to apologize since I was the one who got mad for nothing but she didn’t responded like I expected, I asked her what was going on and she said that we needed to talk, she came to my place and she told me that she is still confused about her ex and that she couldn’t be with me if she still had feelings for him, she told me that it wasn’t me that it was her and that what we had was great and that she loved me , but she still couldn’t forget about him. I told her that I understood and that we were gonna stay friends, it was difficult because I still love her but I decided to let her go and since then I have been out with my friends and I even met other girls, but I still think about her. I haven’t talked to her in a while but deep down in my heart I still want to be with her, so my question is should I stay in touch?? (She wants us to stay close friends) or just move on?? I feel like even if they get back together it won’t last because they were on and off so much in the past. Are they soul mates or is it just that she is still attached since he was her first love?? Thank you in advance for your advice; I really don’t know what to do