1. Forget her. 2. She's not honest with you. 3. This post is wack.
Sorry, I had to do that, just because you told us not to.
Alright, seriously now..
So, you met her when she was 19, and you were 20, if I did the math right. Listen, simply and honestly put, that's just too damn young for anyone to really figure anything out. The chick's going to be confused. It's part of growing up. I'm sure that, at 19 (or 20, whatever), pretty much fresh out of high school, she still had that type of mentality. I'm sure that you did as well, even though you won't admit it.
Now, you've had a year and a half together, plus some. Really, that's not a long time in the grand scheme of things, but at 22, it seems like it. Either way, you two formed a bond that's not easily broken. I mean, she's still trying to figure out what she wants, right? Does she go back with you, or does she move on, or what?
Well man, thing is, she's going to be going through this until she gets it all together - which could be years down the road. An on again/off again romance isn't going to help you at all, you'll only keep hurting everytime she changes her mind.
So, here's my advice: Move on. I didn't say, "Forget her", I said move on. You'll never forget anyone that you've had feelings for, that's impossible, but you can move on and take control of your life. Again, if you take her back, she's only going to change her mind again and leave you hanging. It's better to get your life in order, and let her go so that she can get hers in order as well.
When one person leaves another, someone is always going to get hurt.. Well, usually anyway. What you're feeling is fine, but just don't let it control you. The easiest way to get over someone is just by simply living. In other words, keep yourself busy, go out with friends, go jogging, hell, go skydiving.. just stay busy. Above all, if you still have feelings for her, don't talk to her. Everytime you talk to her it'll only make things worse and you'll never get over her.
It's hard as hell, but everyone goes through it. You'll be fine, just take one day at a time..
I wish ya the best.