Instead of "the talk" think about it as a lifelong conversation. Certainly with 2 younger sibs, she had some questions about where babies come from. Of course you have talked to her about the difference between boys and girls and about parts of your body that are private. I hope you have covered who can touch/see privates and who can't. It is just a continuation . . . she will be curious, you will answer questions. It might come up from something in a movie, a commercial on TV, noticing that an older cousin is wearing a bra . . . Obviously as you start to see signs of prepuberty with your daughter it is time to step up the conversations about washing hair and body, how old is time to shave, starting to wear deo, and what to expect about periods. It can all be a very natural conversation. It can all be very relaxed. You want her to understand little bits of info and come back to you with more and more questions whenever she thinks of something else she wants to know. If you appear nervous/uncomfortable with the topic of her body, she will go elsewhere with her questions - not what you want!
All that having been said, the best book ever is American Girls The Care and Keeping of You! It covers everything from body changes to pedicures. Excellent explanations and very calm manner. My daughter has read and reread it. In fact all of the American Girl books about friendships, emotions, etc are great for preteen girls. Good Luck!
At 11, some of my daughter's friends have started asking me questions because they aren't comfortable talking to their own mothers about this stuff - with three girls, you want to be the mom that is very calm and open to talking girl talk.