The average testing time found in standardization was 30-45 minutes for philly's child's age range, and 45-60 minutes for OP's child's age, but that's for the core subtests (sufficient to obtain the FSIQ, VCI, and FRI). It would be slightly less time for the GAI, and more if you were obtaining all five (three for younger ages) primary index scores.
Although on the shorter end of the expected range, 35 minutes is not crazy if she was obtaining the GAI only. Also, some children do test more quickly than average.
