Hi, Masturbation is common in this age and often, can be taken as normal, although sometimes it occur as part of a psychological disorder. Just be calm, ask what happened, and give mental and emotional support to her as she is already frightened and feeling guilty. Never use any form of abuse. We can convince her regarding inappropriateness of the circumstance in a friendly and phases manner. Since here this happened in an inappropriate circumstance, we have to search thoroughly for any cause. Masturbation of unusual severity or inappropriate circumstances be a manifestation of sexual abuse by someone, accidental exposure to adults having sex, or behavior like porn watching. Kindly take her to a child psychologist, as they are experts in dealing with such situation and can reveal any such cause. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Muhammed Aslam T. K., Pediatrician