As a girl, I'm here to say that first kisses are very significant. They can be filled with a lot of emotion. By one kiss you could be saying a thousand words. And you need to know what that other person is 'saying.' What I mean is, if she acted weird, then maybe it's because you two are on different pages. Talk to her, ask her what's on her mind. Make sure that neither of you are leading each other on, but commited to only seeing each other. Especially if you're kissing. Because physical contact in a relationship makes things a bit more complicated, in my opinion. Just communicate. And kissing isn't a requirement in dating...just thought I'd throw that in there too.