Do not, under any circumstance suggest that she act these things out with you. That is a horrific violation of your role as her stepfather, and the simple suggestion has the possibility of ruining your relationship with her and scarring her for life. If you feel as though you might be "at risk" for her, I would beg that you do whatever it takes to prevent yourself from putting her at risk.

The best thing to do as far as her being active would be to discourage her from this, and remind her of the risk she poses to herself in the form of pregnancy, STD's, and, in her case, the possibility of the dissemination of the pictures. Give her the parental "talk." Nothing more.

My best to you both,
Harley