Q&A: Can Masturbation Cause Physical Damage To The Clitoris?

My new girlfriend tells me that she started exploring her genitalia at quite a young age and that she stimulated her clitoris frequently between the ages of 12-18. She now (age 21) thinks that her clitoris is not giving her the normal sensations when it is stimulated (i.e. she wonders if it has possibly been de-sensitized by the earlier activity).