Invite the girl over to your house & rent the movie "Thirteen". Seriously. I watched this movie with my daughter. Every teenager should watch it - with their parents. It's eye opening and graphic (as in details). I have a 13 yo daughter, too. Her dad didn't think I should allow her to watch it, but I did, and I watched it with her. He prefers to live in the dark and pretend she doesn't know anything about these topics. I keep telling him that attitude is what would get her into trouble. I'd rather be aware of exactly what she knows so I can make sure she knows the FACTS, not what other kids THINK they know as a fact. If you don't feel comfortable watching the movie with your daughter's friend, at least watch it with your own daughter.