Don't know if this makes you feel better, but DD (same age as yours) scored something like 59th percentile on the Quant. section of the CogAT, but 99th+ in the computerized math achievement test done in school. She scored like an average 8th grader. So the CogAT is not necessarily indicative of anything. Do you have a score report? Look at the report and see if it says how many questions she answered. If she is still counting on her fingers to add, she probably ran out of time. You need to finish the CogAT in order to get a high score on it.
Second, have you worked on math fluency with her? Does she know addition/subtraction math facts? Does the school put kids on the computer and have them learn this? If she has not done this, then it makes sense that she is counting on her fingers. If a child is asked what is 7+5 that is something they should have memorized. So (unless you have tried this already) put her on the computer to learn her math facts. Or you can do flash cards, but that is more boring. My kids really like bigbrainz.com (it's like a video game) and it's free for addition/subtraction!
My DD has had a lot of trouble learning her math facts. The psych who assessed her said that it's probably because she's a visual-spatial learner (her non-verbal IQ is a lot higher than verbal) and slow-processor. i wouldn't worry about a disability unless you try teaching her the math facts and she can't learn them.
Does she understand concepts? Like word problems? Why things are calculated the way they are? If so, then that's another reason to not worry about a disability.
