Ok now it's time for a serious reply from my side of the computer screen.
If i were you...i would just let her go and eventually she'll realize what she lost. Don't really keep your doors open or like wait for her to come back, just try and move on. Maybe be single for a bit. After all you are what, 15, 16 ? We are young. We don't need all this relationship crap yet. We've got plenty of time, no need to grow up fast.
Now i don't mean go mingle with all the girls at your school but just be happy being single and being able to hangout with all your freinds that are girls and just have fun. As much as a girlfriend would be nice most relationships last like a month at our age. It's all stupid.
Just ride your bike, play baseball and be happy.
I'm not trying to live vicourisly (sp?) through this post or act like i know everything but that's just my view.