I've done THE talk 3 times with my own children, and other people's children have come to me with questions from time to time, so here is what I think.
No matter what, your daughter will NOT want to talk to you about it. Especially if you bring it up.
Also, the talk isn't going to be the ONLY talk. It is probably best to address things as they come up naturally. I mean, there are several components to it, and new questions will come up from time to time as she gets older. Also, only give her as much information as she wants at the moment. Don't try to overpower her with information. I'd let her know that she can ask whatever she wants whenever she wants. But if you "embalm" certain subject beyond what they are actually wanting to know, she might not ask again.
I also remember my own parents (being in the medical profession) giving me too much information and scaring me to death! I dwelled over it so much, and that was definity NOT the right approach.
For a girl, she will need to know about her menstral cycle, about pregnancy, about sex, about boys, about what is normal to expect as she begins puberty, the physical and emotional aspects of all of it, etc. You cannot have this complete talk in one session, nor should you try.
For us, a book was not very helpful. Different ages are more appropriate for different aspects, and books try to cover too much at once. At the younger ages, she needs to know about the physical aspects of what she will be going through, how she will be feeling, what changes her body will go through, etc. She needs to know about her mentral cycle. She needs to know that 2 years after she begins having breast buds, she will start her mentral cycle. But there are emotions, and pimples, and getting her first bra, and and all of that stuff that will happen first.
My daughter had a lot of questions about pregnancy (as in the specifics of it and baby development) when she was 15, and had a lot of questions about when/if to have sex with her boyfriend. If I had tried to discuss this stuff BEFORE she had questions about it, it would have fallen on deaf ears.
My son had a lot more questions about sex once he went to college.
And THE MOST IMPORTANT thing I want you to hear is that children have more and more complex questions as they get older, and if you develop a realtionship in which your children can always come to you and talk to you about anything, that is the goal. To do this, you have to be available to talk and to listen in all kinds of ways and about all kinds of things. You have to be willing to listen to their lastest invention when they are 7 years old, etc.
My children brought up the subjects at the most odd times, too. A lot of times they brought it up while I was cooking, or while we were in the car together, or right before going to bed at night. They needed to feel that they were comfortable, but that I wasn't able to look right at them. Eye contact is uncomfortable when talking about an embarrassing topic such as this.
We can talk more if you have more questions for me. It is a big topic, but I hope some of this helps.
L.