"He talks about the book to the girl."
Translation:Ele fala do livro à menina.
Well let's say someone is talking with a girl and mentions Hamlet for example, then she says that she doesn't know the book and the guy talks about the book to her. In that case I would say "Ele fala do livro à menina". But if the case is that when he mentions Hamlet, the girl says she have read the book and they exchange experiences and opinions, I would say "Ele fala do livro com menina". So there is a slight difference depending of the context.