The partying I can understand...the 'drinking responsibly' bit...I ain't buying into that. Just a couple of drinks at the end of a vacation & what I would assume to be relatively inexperienced drinkers, would probably be enough to put 3/4's of them under the table.
Some get tipsy, some get sloppy. She was probably just tipsy. I remember back in HS. I was a sloppy drunk. Many of my friends were tipsy drunks. That carried over into adulthood. I don't drink now. Some of them had to quit too, some of them still drink responsibly.