Does your school board require a WISC IV to get into the gifted program or do they use other tests as their first line of screening? What grade does the program start?
What I'm trying to get to is if it is common for them to do a WISC in grade 4 because the gifted program starts in grade 5 then I'd focus on advocating to get her on that list. If however your school uses the CCAT (or something else) and will only do a WISC in the most extreme of cases then I'd probably focus on doing it privately knowing that the odds of being able to successfully advocate for her to be the one in 500 or whatever it is pretty slim since she is at the top of the class and most schools have long lists of kids with more obvious needs. They likely don't care that she should be even higher achieving since they can't deal with that anyway.
I don't know if you can assume it is processing speed/working memory but I can say that my DS (who scores low in both of the above) is one of the slowest writers in his class. Ask him math stuff verbally and he can do it quickly, ask him to do the exact same thing but write his answers down and it takes a LONG time. At school he actually displays many characteristics of ADHD-Inattentive if the work is too boring for his gifted side or too hard for the LD side of him (it's a great combo). The whole reason we tested was because the school unofficially diagnosed him as ADHD.
IMHO most teachers don't totally get processing speed issues (but heck, I barely do and I've been living it for 7 years and reading everything I can so I try not to be too hard on them). The BEST thing having that full report to give to the school is that they stopped thinking he was spacey/rude/clueless/dumb/unmotivated/etc. They don't completely get it but they at least know he is crazy smart so they treat him differently because of that. They also let people scribe for him which greatly reduced his frustration and anger and stopped harping on him constantly to work faster.
