I too have a DD like this - temperamental is a kind way to put it. Have you read Explosive Child? It has good strategies, in addition to Raising Your Spirited Child. Just another kindred spirit on that :-)
As for the test she took, someone else already mentioned the NNAT2 and its limitations. I'll second that -- my DS8 took that in K at 6yo. He scored a 7, which was high enough to make our school's GT cutoff (which, by the way, means nothing - there are no GT services/accommodations). This year, he took the WISC IV through school as a part of broader testing (for sensory issues), and scored well overall, but got his best score on the verbal part of the test - a 150. Without that score he'd barely make the 'gifted' cutoff again. So while he's overall very bright, he's actually gifted in one area - an area which the test he took before didn't capture at all. So your DD may do much better on a different test.
