I'm not an expert, but some relevant things I've heard since having both 2E children WISC-IV tested:

From the Gifted Development Center (http://www.gifteddevelopment.com/):

working memory and processing speed are not highly correlated with giftedness. In their research sample of gifted children, mean scores were:

Verbal Comprehension Index: 131.7
Perceptual Reasoning Index: 126.4
Working Memory Index: 117.7
Processing Speed Index: 104.3
(I notice that the 1st 2 are using the WISC-III names, but seems to be talking about WISC-IV anyway)
http://www.gifteddevelopment.com/About_GDC/whoaregiftd.htm

A difference of 23 points or more between any 2 of the 4 composite scores means the FSIQ is "not interpretable" and should not be used.
http://www.nagc.org/index.aspx?id=2455
The Gifted Development Center recommends always using the GAI instead of the FSIQ to determine giftedness.
So, ignore the FSIQ for your dd.

If subtest scaled scores differ by 5 or more points, then that composite index is not interpretable, and should not be used. So, your dd's perceptual reasoning index is not interpretable, and the individual subscores should be considered instead. This information is from:
Essentials of WISC-IV Assessment
By Dawn P. Flanagan, Alan S. Kaufman
I think this means that the GAI isn't even considered a good measure for your dd.

by age 9 (not much older than your dd), gifted girls may be socialized to hide their abilities and may be unwilling to guess, both of which will adversely affect IQ scores.
http://www.gifteddevelopment.com/What_is_Gifted/learned.htm

from my experience:

some testers would've used the scores in parentheses instead of the lowest subscore for VCI and PRI, which would significantly raise these scores (another poster mentioned something like this). this substitution is supposed to be decided before testing (of if there's a problem with administering a subtest), but there also shouldn't be a huge difference between subtests.

I was told that auditory and visual processing problems could affect verbal and performance/perceptual composite scores, respectively. So, your dd may in fact be far more "gifted" than the scores indicate.

My ds had top VCI scores, but 80 processing speed. Even though you wouldn't expect a "gifted" child to have PSI much above 100, this is still considered quite low, and maybe 88 would also be. DS apparently has both visual and auditory processing deficits (visual has been confirmed by a developmental optometrist, auditory is far more apparent but never taken to a specialist). He also has visual-motor deficits (why he always hated drawing assignments). He now has a 504 plan that specifies:
. he can type instead of write (addresses visual processing deficits)
. he does not need to draw, but can use computer art, highlight borders instead of coloring maps, or omit drawing portions of assignments (visual-motor)
. get written notes from teacher or other student (auditory)
. preferential seating, not necessarily front row (visual, auditory)
. get instructions repeated when requested (auditory)
. time and a half for tests
. do half of homework for full credit if he shows he understands material

This last "accommodation" isn't standard, but we convinced the school it was warranted because of his giftedness-- he does *not* need as much repetition as other students (I've read that some studies show that gifted children remember things less well if they're repeated more than 2-3 times!). Doing well on tests proves that he's done enough homework. I've listed these in hopes that it may help you if you work with the school for formal (IEP or 504) or informal accommodations.

Hope this helps.