You need to play this right. It is obvious to me that this girl has an interest in you. Crush is a scary word for her to be using. It should be interest, not crush. People with crushes sometimes become weird-o's.
I would ask her out on a date and see what developes.
Throw caution to the wind because if you let your low esteem get the best of you then you masy miss out on one of the most exciting times in your life....dating.

Go have fun and be safe.