Isn't this the hardest? I am a social worker and I always feel like I should be able to handle difficult situations as well as I do while working. Luckily my nieces and nephews are 10 and younger and not quite at the stage as your niece. But, my 16yo cousin is. It seems quite mainstream these days for girls to act more sexual than their age. They are rewarded for it in their high school society. My cousin's facebook page scares me sometimes and I clam up trying to figure out how to handle it. But, I feel strongly about not violating her trust (she allowed me as her friend) and going to her parents. Although, if I felt she was in any danger I would have to. Maybe you could find information that you could email to her with a note such as: This is difficult to talk about, but I care about you and I want you to always respect yourself and be safe. I'm not sure I have the answers, but I can tell you that I relate. Wishing you good luck with this.