Angelina
Simply not being directly harmful does not mean it's fine or even necessary to allow. Unlike boys, girls almost never have a valid reason to touch there, especially when a bidet is available. In almost every situation, when a girl touches there, it would be better if she didn't or couldn't. That's why a girl doing anything involving her private area should require permission first.
Back when I was 14 I did not know about masturbation or orgasms. Still, I wish I had a belt back then, it would have been good for me.