Most Helpful Guy
@Raciocinative has it spot on.
Just move on and have fun, if she changes her mind, she knows where to find you.
Just let her be and chalk it up to relationship experience. Your young, chances are you will find better anyway, most people always do.
Maybe think back to any faults you might have and improve yourself, it's always a good start.
Worst thing you can do is chase after her or beg, just leave her completely alone. If she still has interest, she will reach out once she is curious enough about you, than its a new game, the balls completely in your court.