Can you get the CoGAT done privately well in advance for much less money than a WISC 4? Is you daughter 6 yet?
Seems like trying to time the CoGAT is too stressful - especially in a family where one kid has 2E issues, I'd get the private WISC 4 as soon as the 6th birthday is here.
It is so inevitable in families that parents will compare one kid to another informally - A is so ahead in X ways but so behind in Y ways. I think having official test scores makes this natural but uncomfortable comparing better. One can say 'well A's processing speed is so much slower, I'll bet she knows the answer, but needs a while to think about it.'
Just a thought.
Grinity