Thanks for this question. It is hard to understand exactly what you are describing, and speaking with your pediatrician
or an OB/GYN would probably be a good idea to make sure that this is not something significant. While there is erectile tissue in the female reproductive system as well as there is in the male, it would be hard to just discount her symptoms in that manner without understanding more fully the problem. There are other things that could be causing these symptoms, and some of these may be serious although it is hard to clarify this in this format. Please have her speak with a doctor
and get the answers to your question.