Where I live, providing a place for minors to drink is illegal. It doesn't matter if other numbskull parents brought their children over to drink as well. A child may have alcohol supervised by her own parents, not someone else's. Perhaps I'm not understanding. The other parents don't have to be present when their kids are drinking?
I would certainly talk to her about how alcohol and pot lower inhibitions. And also, no one deserves to be raped, but that is exactly how a lot of rapes happen. Expecting drunk, horny, teen boys to stop when she says no: They SHOULD but very often they don't.