First let me say, I am so sorry! This sounds like a very stressful situation.
Obviously there are a multitude of possibilities, and I wouldn't underestimate the effects of allergies/allergy meds. However, reading your description I'd look more toward fatigue (mental rather than physical) and control. When did she make the move to accelerated afternoons? How do these afternoons compare to the previous situation? It is possible that moving from afternoons of self-directed play to afternoons of prescribed academic activities is causing her a great deal of mental fatigue. Even if it is intellectually below her level, operating under someone else's directives, rather than your own, can be exhausting in it's own way. I know I can be easily exhausted when I have to be "on" for long stretches of time. It's also a big loss of control in that she's presumably having to follow someone else's lead for a much larger portion of the day.
Just some thoughts, but I could be way off base! I hope you get some good replies that help you out!
