First off, welcome to VT!
So anyway, are you emotionally attracted to girls? Like, do you love their personalities? Whether or not this is a yes, based on the info I could say that you are a lesbian.
Secondly, about your parents. I think that they are in denial if you explained it to them and they didn't believe you. Of course, they might have just thought this was recent and really believed that you're going through a stage - everybody does.
And last, about your crush! I think you should get to know her, and have fun with her during the summer. I think you should stay friends...and then you could come out to her once she really gets to know you. After that, once she's comfortable with it, you could tell her you like her.
I would tell a guy that I like him, and then I'd say if you're straight (or if they're seeing someone) then I'd say "I just had to confess, but it's ok and I'll accept that we won't do anything. Still just friends?
And that's my opinion. I hoped this helped in some way, and please answer my question!