Are Vampire Diaries books okay for an 11yo?

If she is mature for her age, I don't see it being a problem. Reading anything is never a bad thing. Reading raises awareness, questions, makes one think. As for the more adult content it might contain, she may understand it, may not but I don't see it being harmful. It's all part of growing and learning, even in a fictional story. At her age, the more adult stuff may just digust her, in which case she will throw the book down anyway. I say let her read.