Update to this post.
So, there’s some good news: it turns out sister’s BFF didn’t have a BAC over the limit. As in, maybe she had a few drinks, but she wasn’t drunk. So, no one is really sure what happened now—maybe she was distracted by something? It was a sharp curve on a two-lane road, and she swerved over the line coming out of the curve, which caused the head-on collision. The kids who died were not wearing seatbelts. BFF was (and she was alone), and 2 of 3 people in the other car who survived were also belted. (WEAR YOUR SEATBELTS, EVERYONE.) So now the police are saying they don’t think it was “criminal” in nature, which we think means she won’t be charged.
Also, BFF is still alive. We’re not quite sure HOW, because it turns out she had/has a bunch of internal injuries and likely should have died at the scene—the ligaments connecting her neck to her head were severed (which, omg creepy, and also about 85% of people do not survive that beyond the accident/subsequent hospitalization). She had surgery on that, which apparently went well. She also had a ruptured spleen and still has a hip fracture, skull fracture, shattered knee, and brain swelling. She is sort of awake from her coma and responsive, but not fully awake yet.
So, in short: still alive, and chances are she will not be going to prison. But holy shit, what a terrible accident. Sister is holding up well enough—I did send her a care package and she was super appreciative.