Patricia's comments about food additives reminded me of a conversation I had with a parent of a child in my class one year. Her child had a food allergy which drastically affected his activity level and focus in school. I can't recall exactly what the food group was, but for some reason wheat comes to mind. It was one of the questions I had for Ryleigh's pediatrician, as we determine whether she suffers from ADD (at this point, we're working on the assumption that she has a mild case of ADD and doesn't need medication, thank goodness). Perhaps monitoring your daughter's food to see if anything causes her to be more active in the evenings. Indeed, articles I've read in some of the teaching journals point to food additives as contributions to hyperactivity.
I do also have to say that I was one of those kids who rarely need a full 8 hours of sleep. It used to drive my mom crazy because she was BIG on sleeping.