The GAI is an index that's includes only the scores that are considered more indicative of giftedness.
Though, I just realized, with a 4yo you're talking about the WPPSI, not the WISC. The WPPSI may not have a GAI. Oops! I'm not sure about that!
Sorry to confuse things!
Wait until she's 6 and you can have her take the WISC, if you need more info. Or after 5, she could take the Stanford-Binet. And there are a number of achievement tests she could take.
But unless you need more info or think that there's reason to doubt these test results, I don't know that you need to re-test. Testing for the sake of testing always seems sort of wasted to me. But that's just me...
