At our top-ranked local public high school, they say there is supposedly 3 hours per night per AP class! Some of the Tiger Mom kids take 3 AP classes at a time. AP classes here are weighted as a "5" (if you get an A), whereas regular classes are weighted as a "4" for an A.
The average GPA of accepted students to a UC school last year was 4.20 on a 4.00 GPA scale. How can that be??? Maybe part of what you are seeing is that she is young for her grade, with grade skips, and she is not able to keep up right now with the busywork that comes with these higher level course?