Thanks again Grinity--
Saw this on another thread, aculady's words, but this seems totally like my dd, and IMO would also have been a factor in her performance:
"Another thing to think about is that lots of gifted kids really dislike being asked to demonstrate their knowledge just to "prove" that they know something or can do something. If your child can count, and has shown you this before, he may "guess wildly" because he is feeling insulted that you think he can't, or feeling resistant to be being asked to "perform", or because he thinks it is funny to give an obviously ridiculous answer."

I guess time will tell. While dd10 is pretty intense, she seems to be optimally gifted and I get her and get how to help her and it seems pretty clear how to advocate for her. Dd4 is a conundrum to me--I think I was hoping having her tested would explain some things but I guess there aren't any easy answers with kids.