Hi M.,
The two best books out there on the subject of sex and puberty are "Where did I come from" (sex and babies) and "What's happening to me" (puberty). My mom got these books for me and I devoured them. I, in turn, let my sons (11 and 14) read them.
If you don't want your daughter learning from her peers then you need to talk to her openly, honestly and answer all her questions no matter how bizarre they seem. As I told a friend recently, freak out in your bedroom closet when the house is asleep. Here's my story...
My oldest son came to me with sex questions when he was in upper elementary grades. I answered with a fairly straightforward, "scientific" answer first and addressed all questions. Once that was understood, I put a values discussion on top of it so my son would know what his father and I thought was the "right" thing. Over the years, both my sons have learned that they can ask me ANYTHING and I'll answer to the best of my ability, no matter what.
This scenario really tested me when my 15 year old was in 7th and 8th grade. Turns out, I was one of the few moms who would talk openly about the subject and his friends knew it. He would come home with everyone else's questions for me to answer and then he'd report back to his friends at school. I couldn't believe my ears when he told me that. Because my sons know they can ask anything the "word on the street" is taken with a grain of salt.
But, I have sons. Would a daughter be different? I was a daughter once (still am!) and my mom did the same thing with me as I do with my sons, so I guess it works for both genders. And, if I couldn't ask my mom, I could always ask my grandmothers. That was interesting...the "skip a generation" approach.
I hope this helps. Good luck!