It seems to me something affected her judgement that day, way beyond the usual course of things in her life. I think this because it has been stated that she had an unblemished driving record, and none of her family seems to have been aware that she had an alcohol problem (I'm assuming for the moment, that this is true). This says to me that, assuming she was an alcoholic, she must have had pretty good control over her drinking, and decent judgement, at least decent enough not to get any DWI's or act in a manner when intoxicated that would give away her *secret* drinking problem.
So what made this day different? There really COULD have been something physically wrong that, coupled with her drinking problem, led to such a tragedy. Maybe she was planning on having a couple of drinks of vodka on her way home, to relax her, and maybe to smoke a joint... Maybe this had been her *usual* practice, have a drink or two of vodka on the ride home from camp, maybe she had done that for a while on her drives home, had just a bit of vodka, enough to relax and make it home with the kids unscathed. But, if something was physically wrong with her that fateful day, it could have affected her judgement causing her to drink way more than she had ever planned on. The fact that she called her brother like she did makes me believe that this is a possibility. If she was just drunk and smoking pot, why would she call her brother?
Things that could have have affected her that come to mind are:
1) Some physical illness not easily detectable through standard autopsy tests.
2) Some kind of poisoning that doesn't show up on a regular tox screen.
3) Some kind of psychological "break" with reality. Could she have had some kind of mental breakdown?
It seems to me whatever happened that day, there is more to it than her just going on a binge that sunday morning. I really think they should do another autopsy, if there's any possibility of finding an answer, it should be done.