The WIAT and the WAIS are co-normed, I believe so that might be a good way to look at discrepencies btwn ability and achievement. However, given what you say about her achievement level, I'm kind of doubting that she'll show significantly lower achievement than ability.
Is her vision correctable enough with glasses that she won't be disadvantaged on the parts of the test that require visual acuity? I'm thinking of the block design test and the processing speed tests that require one to be able to see reasonably well.
Can you ask them about their experience with gifted teens/kids before you commit to testing there?
