Thank you all for the replies. The article on stealth dyslexia is very interesting and provides me a good avenue to pursue for her. I see some hints of her issues in there, although she so far would appear to be a very mild case. She is left-handed, which we have assumed is the reason she has had to work hard at her handwriting, but that article has me rethinking that assumption. Again, maybe it is that the work hasn't become too challenging, but she excels pretty much across the board, including on spelling tests and in math. It is only when she does independent writing that the spelling errors appear, and although I think her rote math memorization is weak, it hasn't hindered her school work at all. In fact, my husband questions whether I am making a mountain out of a molehill over this. But my daughter does have a strong perfectionist streak and is easily frustrated, so I feel that it is well worth the time to find any tools to help her fully utilize her strengths.
Regarding the extended norms, would the psychologist have these if I asked at this point for them or does it need to be captured and scaled at test time? She wants to do achievement tests (I think verbal and math) and the Stanford Binet IQ test. I understand that the achievement tests are to look for a gap between ability and achievement but am not sure that is the best next step (if she doesn't make it into our GT program, we'll do them anyway for an appeal). I am really interested in what I've seen on other threads about needing to have a psychologist skilled in gifted issues do the testing. How would I go about finding the right tester? This psychologist came recommended from several people for being experienced and well known to my school district but I don't feel she builds in the discussion time and analysis we would need. Her written report was even less informative than the 7 minutes of oral explanation she gave me.
Since you all have been so thoughtful in your suggestions, I will give her teacher's point of view in case it helps round out the picture. She has a very experienced teacher who said this upon seeing the CogAT and NNAT test results (and before knowing the WISC-IV results):
"Personally, I think DD possesses unusual qualities for a typical 2nd grader. She enjoys adult humor and company. She'd rather read than play, but is not averse to play. She shows "out of the box" thinking. DD is quite talented in language arts, though her spelling can be pretty bad

. (She has a tendency to transpose letters and I've discussed this with her.) Her reading comprehension is unbelievable and she has an uncanny ability to inference and predict using that superior level of comprehension."
I think it is because the psychologist commented on things that have been in the back of my head for a long time, and that she did so with such strong authority, that has me feeling that there might be something neurological going on and potentially be ways to help. The Stealth Dyslexia article confirms that there is more to look into, if even just to rule out, but I am not sure where to turn to do so.