Talk to her about it. Don't be shy or worried- it's natural, and be as straightforward as possible. It is a big mistake to let them figure it out for themselves. You are a parent and are their guide to their body and relationships and how to interact with their world. Be sure to use movies and tv as an excuse/launching pad to talk about appropriate/inappropriate behavior between the sexes. Since your daughter is developing early it is especially important to clue her in on the ways boys will try to appeal to her, flatter her, and their motives even if they themselves don't know what they are. Knowledge is the best defense and if you are frank and unashamed, she will be more likely to approach you if a question or issue comes up. Good luck!