J.H.
After reading the other response, it reminded me that my daughter had an 'incident' at a sleepover where the girl wanted to take 'sexy' pictures of each other. My daughter went along for a while, but it made her uncomfortable, so she enventually snuck into the closet to call me from her cell phone. Which leads me to that point, I gave her a phone so she could always call me without having to ask to borrow a phone. We had moved also, and I didn't know the parents as well as I used to, so I felt more comfortable with her having the phone. I tell everyone to give their child a phone for sleepovers - it's quite reassuring to the child. J.
Don't worry about it. My daughter is 9 and she has several friends who don't do sleepovers, and I had one in bed with us as recent as last summer. They have many more years to do sleepovers, don't push it. They have to grow up so fast in so many ways, let her be a little girl in this one area. I know it's hard when other kids are going and going, but just enjoy her for now. She'll be out and about all too soon... J.