I think that your concerns are normal but to some degree, so is her behavior. First, I would try to think back to when you were her age and when you had your first "boyfriend". Mine was when I was 7 or 8 but that meant you'd smile at each other, sneak tic tac toe notes and always choose one another first for monkey bar races (and I did like boys before that). It was very innocent. And just because she's interested, it doesn't necessarily mean that she'll be an early bloomer (although she could)...I was very a late one!
What I would focus on is that she learns to prioritize social activities and school activities and learn when it's appropriate to discuss personal things. It sounds a lot like she's trying to practice at being grown-up.
Another suggestion is that you may want to take a look at her external influences (maybe you already have). I'm not saying keep her completely isolated - it wouldn't be possible and she'd resent it. However, maybe you should watch a few episodes of whatever show it is that you allow her to watch. Many of the kids shows today have older children who are dealing with "relationships". She may be modeling what she sees. Same goes for music (the lyrics can be really inappropriate sometimes). Anyway, I'd recommend that you participate in some of these activities with her and then discuss it with her. Take advantage of the fact that you have a lot more influence over her now than you will when she's a teen. If you talk about what you liked that you saw, what you didn't like and what could've been done differently, those impresssions will stay with her when she's older and making decisions for herself.
Good luck to you! My two are each a year behind yours so hopefully you'll find some advice that works for you and then you can give it back to me next year when I start to worry about the same thing :)