Little Details

First part of the question: what refreshments are likely to be provided after a graduation at an Ivy League College? (At my university it was strawberries and cream and tea-or-coffee and possibly cheap booze; it was meant to be a garden party and ended up being a tent party :) )

Assuming that there is champagne or something available (it doesn't have to be at a university-hosted event, I can work around it, but I'd like it to be if possible), and the parents and the twenty-one-year-old are standing around drinking and laughing. 21 starts teasing the sixteen-year-old about being left out (it's his graduation, btw, he's a child prodigy). In Britain, it would be entirely plausible for one of the parents to say, "Well, two sips aren't going to turn him into an alcoholic." How likely is this to happen in America? (Background info: It's early 1990s, they're from California, they're currently in New Jersey, the parents are Baby Boomers, liberals, ex-war protesters and non-practising Jews. Mom's a lawyer, if that's likely to make a difference.)

I've Googled underage drinking + America, graduation, graduation + alcohol, but I' getting lots of 'don't let your kids do this' which is not what I want.

I have a bit of an odd question, I think, but I can't figure out where else to ask.

Setting: US (New England area--small but fairly liberal town), contemporary

I'm working on a story with two teen girl main characters who were once close friends and are now enemies. One is popular and the other doesn't care at all about social status but is involved in sports and a few extracurriculars. If the popular one wanted to start a rumor to ruin the other girl's rep, what kinds of rumors might she start? I'm SO out of touch with teen life today. I feel like back teens are so much crueler now than they were when I was in high school and I can't drum up anything awful enough!

I've done my best to google, using terms like rumor + enemy + high school, and ruined reputation and the like, in all kinds of configurations, but no surprise, no one is exactly documenting this kind of thing.

Thanks!

ETA: I'd prefer to avoid the lesbian/slut option if possible. Getting into why would be complicated to explain without going into my whole plot, but they don't quite work for what I'm going for. I also want to avoid hard-drug-related rumors. Just about anything else is workable. And I do know that it's likely that people won't believe the rumors 100%, I just need enough to get people talking about her and making her uncomfortable in school for a few weeks.

Edited again: Thanks guys! I think I have what I need. You've all given me some great ideas and pointed out some factors that I might have otherwise overlooked. Everyone's input has been very much appreciated!