My daughter has a friend who has visited a cyber sex website. I'm not even sure what this is exactly. Is it a chat room? If I tell the girl's mom, then I'll have violated information that was given to me in confidence. What should I do?
This is not an issue of confidentiality as much as it is an issue of safety. This girl's mom needs to know that this has happened in order to protect her daughter. There are many variations of questionable websites, and they can range from chat rooms, to sites that exhibit pornography (or child pornography) to sites where adults get a turn-on by encouraging children to visit.
Talk with your daughter and her friend and let them know that you are worried about her safety. Explain that the friend is not in trouble, but that her mom needs to know that she has engaged in behavior that is not safe, whether it was on purpose or by accident. Offer to help the friend talk with her mom about it, and make sure that both girls understand that they should never visit a site like that again.