hi I was "abused" when i was five and i .... :( did the same thing when i was 11 my sisters mother cough me and my family discussed about it like they where angry or something... my father told them it was normal but my mother and sister wanted to take me to a psychiatrist. And they made me feel bad when they discussed about it(yelling at each other) like i was the reason why i made them angry :(... just talk to her. discover why she is doing it with professional help mostly,maybe you will found out, and she will open up to you or so i hope... they never asked me the question and i didn't got the chance to speak or to be heard. don't make the silence for her. please :´( hope this helps...
My concern is your statement:
"... terribly exposed to sexual activity done by others...."
I'm not sure what this means, but it sounds like she may have been sexually abused, which very well may explain the behavior you described in your post.
She should not be disciplined for this behavior. Rather, it sounds as if she needs counseling to first determine if she was sexually abused with subsequent treatment.