A fellow New Englander! I no longer live there, but I too grew up and partied wicked 'hahd' in rural New England. I'm a Boomer. But just like you describe, this was the way folks socialized, acted out, and managed emotional pain and angst.
There was no internet, no cell phones, etc. We heard about where the parties were each night by word of mouth or good 'ol land lines. We drove in all sorts of states of mind, often with passengers, and most not wearing seat belts back then.
Some raced on back roads late at night with no fear, including myself (a teenage girl then). And sadly for a time (circa 1976-78), it seemed like we lost a friend almost every weekend, or at least once a month, to a fatal accident.
So back to dear KR. I am not wasting my time pining about these kids partying in the woods, or how their parents enable or are ignorant to that behavior. To me it seems strangely familiar. Having been in KR's shoes, I am trying to figure out what she did around 12:15 / 12:30am that night - and why no one has said anything? IMO, she was simply going home alone.