While one can argue if rape fantasies are normal or not, what I am concerned about is a 24 year old female is having these fantasies as a victim pretending to be a child. I think this warrants some concern and you should talk about this to a therapist and get their take on it. I'm worried their are some underlying reasons for these fantasies, specially being a child victim. I am not judging anyone here, but I do see reason for concern and it should be discussed further with a professional.