I teach high school. Usually when the kids have these sort of parties they stay up all night talking and goofing around. The kids that want to "hook-up" are finding ways to do it and don't need a party as an excuse to get together. If your daughter's values and self-esteem are intact, she will probably be fine. If they aren't then it's probably too late at 17. Have a talk about what you expect of her and trust her.