What happens next?

How to tell your girlfriend you are not a lesbian
Gather up your knowledge of this girl you've become smitten with.
You're going to have to think of the least painful way to break it off, and only you will know how.
Find a secluded place where there won't be any onlookers.
You don't want a public scene-you don't want to embarrass or hurt her any more than necessary. Try to find a place that doesn't hold any loving memories; that will make it harder on both of you.