At 22, it's really hard to want to commit to something permanently (I think you get this, from your other thread). When I was 22, I'd been with my bf for 5 yrs already and I remember thinking......is this it for me? Am I going to have to marry him next? The idea of that type of FOREVER at such a young age was terrifying, and quite honestly a little sickening. We broke up, and it was the best thing I ever did....sorry.
You guys are in very different life stages. You're ready to settle down into something permanent, and it sounds like she's not. Respect that even if it hurts. Give her the space she needs. If she doesn't come back, at least she's been honest, at least you know the breakup was amicable and for good reason. That's not going to make you feel any better, I know. You can't force someone to want to be in a relationship though, you have to let her back on her own terms, only if SHE is willing. Don't break down and beg (girls see this subconciously as weak and therefore unattractive).
Good luck.
Live as if you were to die tomorrow. Learn as if you were to live forever. - Mohandas Gandhi