Taurus,
Let me tell ya the best advice I can give you that was given to me a while back. LIVE YOUR LIFE LIKE YOU TWO WILL NEVER GET BACK TOGETHER. This will allow you to move on in the best way possible and if you don't get back together, you've prepared yourself for it. If however, you do get back together, that's just a huge plus you weren't expecting. If you keep on dwelling on this girl without trying to move on, you will stay in a continuous emotional spiral that will take a long time to get out of.
Two, as hard as it may be to do this (believe me, I've been there twice), break-off ALL communication with her. You CANNOT be a friend to her right now. All the continuous talk with her will get you is depression. IF you don't get back with her, time will heal your wounds and THEN you can be a friend. NOW isn't the time because there is too much EMOTIONAL feeling for her. For example, when I've gone through hard break-ups in the past, I'd go several days w/o talking to her/them and I'd start feeling better. Then, the instant I heard her voice on the other line or saw her face, I was right back where I started... YOU CANNOT MOVE ON LIKE THAT BRO.
Third, as long as she can have the best of BOTH worlds, why should she choose you man? I mean, right now she has this other guy, but she knows all she has to do is snap her fingers (no offense, I've been there) and you're there. So, let her know what it's like for you to not be there waiting on her and see if it changes how she feels about you. By doing so, you are moving towards a recovery and she is forced to make a REAL decision about her feelings.
Lastly, you guys may not ever get back together and that might be for the best. Although I don't pretend to be a portrait of Christianity, I do know that God IS the answer to alot of problems bro. HE can see the big picture when we cannot. Right now, YOU CANNOT because you are hurting and that sucks. If in my past I would have gotten my wishes and been allowed to stay with the girls that I was hurting over, I'd be robbed of the blessing I received when I met the girl I'm dating now... the best person I know. I'm not gonna throw the "there are many fish in the sea" analogy at you because that doesn't help the way you feel in times like these.
In closing, the only things that can make you feel better is TIME, God, and a new chick one day. But make sure you close all ties with her for now buddy. If you wish to discuss any of this further with me, email me. I hope this helps and sorry so long.