The achievement testing will help you more with the teachers anyway. "Reading at the 8th grade level" they all understand. "GAI of 127" is Greek to most of them. (Not that I blame them--it was Greek to me until I started hanging out here!
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I'd trust the achievement test over the IQ test, since that lines up with your experience, too. I think I'd approach it from just what you told us: She is...
a kid with an ability to read at 8th grade level (from her lexile score), has low-average processing speed (in real-world stuff, it's probably even slower than what her PSI suggests), and is a very private/perfectionistic child
If you don't trust the IQ test scores--and I don't, given what you've told us--then I don't think you share those. What's to be gained? All the teacher will see is "not GT" (if she sees anything at all), and I don't think that's accurate. It's certainly not helpful to your DD.
