Masturbation is normal, but it can be difficult when discovered by a parent. The mother should approach the situation with empathy. She can start by assuring the girl that she loves her no matter what. Then, she might want to educate the girl about appropriate places and times for personal activities. It's also a good opportunity to teach the girl about body respect and privacy in a more general sense. This can help the girl feel less ashamed and more confident in understanding her own body and boundaries.