In this day and age, I'd say class rings are fairly insignificant. I'd save my money on that one.
I'd also spend some money on portraits, but you don't have to consider them "senior portraits". You can then get them done again at 18 when she's graduating college.
She's probably pretty safe at a school sponsored party. The chaperones are usually parents keeping a very watchful eye. Probably not even a chance to play spin the bottle or truth or dare. (which there might be at someone's birthday part or something, where the parents let the kids all hang out alone in the basement) If you let the chaperones know her age (if you feel comfortable) then I'd expect them to be all over her even more.
But all of this really based on her feelings. If she cares about it, let her do it. If not, probably a waste of time/money.
