I agree with all the good advice given here, and I also had another thought: When you called this girl a lesbian, is that because you knew, absolutely knew, that she was a lesbian, even if she didn't know it yet? I'm guessing the answer to that is probably no. There is no way that she could know if someone is a lesbian if they don't think it themselves, and she can't make you a lesbian by calling you one either.

I've got to say though, everything you've said here, it sounds to me that you're straight. There's no reason you have to have it all figured out now though. There's no deadline for working out what your sexuality is. If you're attracted to someone and want to date them, go for it, and if it feels right, then you'll know.