Yes... sigh... anxiety-ridden kids are so prone to being chameleons. I've mentioned in previous posts about how, once my DD realized she was the only one in preschool who could read and write, she suddenly "forgot" how. She and I both have been slayed by the perfectionism that Dude mentions.
What test was it (i.e. WISC-IV) that gave you her IQ score? FWIW, I don't think false high scores are possible. Many issues can interfere with testing and create false lows, but not false high.
Funny I thought that 130 was where gifted started (as in MG, not HG). It's true that there are different definitions though.