I don't like how you already viewed it as to going back to square one and lost all your progress. You guys have dated, broken up, gotten back together to the same result. If those kind of issues aren't addressed, put behind you, and you haven't been on your own long enough to mature or change, getting back together now would be a crazy mistake and would end the same way. You make it sound like moving on is the end of anything in the future, when you have so much life ahead of you to live and there is always a slight chance you guys could end up together in the end. It isn't likely but you have no way of knowing.
To rush back into something could be a terrible mistake if it's too soon. The more times you break up, the more it's going to be engrained in your heads that it can't work out. It's a delicate situation I wouldn't want to try again right now. You can speak for yourself and her progress, but what about her? It's going to take both o you. You have no way of knowing if she's ready (even if she says she is, it could very well be out of lonliness). Time is your friend here and while it's true that she could find somebody else in the meantime, it's not likely that it's going to be the person she is going to spend the rest of her life with. Remember that no matter how it works out, you will be okay and you will find somebody in the long run, whether it's her or somebody else. Push forward with a little confidence and see where you are in some time.
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.