Sounds like you have a lot of different smaller or medium problems adding up to one big one. Can you break them down and try to address them singly? For example, your idea of math acceleration fixes one discrete problem (math is too easy at current level) and will have a bonus of easing overall boredom-related stress while also exposing her to other kids.
I know about the leave-it-blank or ignore-it thing. I'm seeing it too, and need to discuss the issue with one of my son's teachers. I wonder if it comes from being tired of doing the same thing again and again.
I remember once in 7th grade we had to take a math test: 50 problems, and they were all the same; convert a decimal to a percent or a fraction and vice-versa. That test was so boring, everyone in the class stopped caring that it was a test and most kids shut down. Fifty of those problems was just too dull and no one could focus after a while. There were lots of blanks on that test (even though all the problems were at the same level of difficulty) and our teacher got really angry at us. He just didn't get it.
