How confusing and stressful this all must be Pemberley - it's confusing enough to me just trying to keep track of everything you've written, I can't imagine how frustrated you must feel when it's your own child! I wish we could all give you a huge cyber hug.
I agree with DeeDee's suggestion to try to find a local parent's support group and ask for advice their re experiences with local neuropsychs. The other thing I'd consider doing is going back to the school district with your medical eval results and if you can get it, a letter from the neuropscyh you talked to on the phone who has questioned the large discrepancy in your dd's first testing. I'd request a follow-up eval through the school district based on the input you've had from medical experts and the other neuropsych. You won't' get that eval (most likely) until late spring or early next school year, but you'll get your request on the books.
When you run up into that brick wall of "can't re-test within 12 months" there *is* a way around it - using a different test. It looks like the big question is with the ability test scores, not the achievement tests, so I would try to find someone who can test asap using a different IQ test - that should be something you *can* do. Most likely you can't do that through the school district because I suspect they only use the WISC, although they might be able to administer one of the group IQ tests that are used commonly for screening for gifted programs in early elementary - that wouldn't be the best answer (as far as I know) because you wouldn't get as much detail, but it might be that if there is a huge gap it would show in some way on those tests. I think the best scenario would be to find someone who can administer either a form of the SB or the WJ-III Cognitive Abilities test. Our 2e ds has had the WISC twice and the WPSSI before kindergarten privately, and the WJ-III Cog through a school district evaluation. Although his gap is in a different area then your dd's (it's all in processing speed), he has a large gap in scores. The key thing is - it is consistent throughout each of the IQ tests he's had over the years, which helps confirm it's not the result of anxiety or distraction etc on the day of the test. One more test for your dd could help answer that question, which would allow you to move on, so that would be the primary thing I'd be looking for at this point, either through the schools or privately.
The other thing I'd do is go back over yourself, what types of troubles (not just her migraines) your dd was having in school last year and this year, when did they occur, what activity was happening, where was she, every little detail you can think of. Look for patterns, go over again what appear to be the issues - to you - then take a close look at the abilities tested in the parts of the WISC that your dd's scores are low in. If you see a relationship, don't be deterred by a professional who says the gap is too large - what's more likely in that case is that your dd really is a very unique individual and unique enough those professionals just haven't seen anyone with a similar IQ profile.
I'll also add another thought - as parents we tend to worry about, are we going to find the best professional to test, will they be familiar with gifted children (or whatever else is in play with our kids), will they take their time and do a thorough eval etc. When it comes to taking this next IQ test, my honest opinion in this case is that - as long as you feel you've got a competent professional, don't overthink the choice of who, just try to get it done. If it really was anxiety or some other off-thing that impacted your dd's test scores the first time around, then you'll see a very different profile whether or not your dd is tested by the best neuropsych on the planet. If she's got a true gap, that's going to show too. In my ds' testing, we had tried our best to get him a good's night rest before his private appointments, and made sure he wasn't stressed out etc. Then when he was tested at school - yikes. The school wouldn't tell us when they would test, but we didn't realize that - we thought they'd let us know when, and we were also used to the school moving *very* slowly on things. We'd just come back to school after Christmas break, and at our ds' school those first two weeks are a special class time where kids get to study a class of their choice that's outside the normal curriculum and in general something they really really enjoy and want to study intensely - that year our ds had an astronomy class which he was *loving*. One day after school we went ice skating which, at that point in time ds loved. Then he got run over on the ice by a huge adult, took a hard hit on his head plus bit through his lip to the point we considered taking him in for stitches. DS was screaming and had a horrible headache that night which we had a tough time giving him enough pain meds to even get to sleep - he kept waking up all night. Plus he was so freaked out by the accident he kept remembering the big guy plowing into him, over and over and over again. I think he slept for maybe 2 hours max all night, then had to get up and go to school again and then.... you've most likely guessed it by now... he gets to school, is in this way awesome class he's so enjoying and that only happens for two danged weeks and sure enough, he gets pulled out for his IQ test. ARGH! My normally very laid-back mellow ds was sooooo beyond mad about getting pulled out of the class that he spent the next week complaining about it and would still bring it up even more than a year later if there was ever any mention of anything to do with his IEP etc.... clearly not the ideal scenario that I as a parent would have picked for my son to take an IQ test! But.... I mention all that because... his IQ scores were still consistent - the highs were still uber-high and his low was still totally completely obvious. So - absolutely try your best for a good test situation with a good psych, but also don't overthink it - if there's a gap there, it's going to show.
Last thing - I'll have to go back and re-read what your neurologist said about seizures again and why they are convinced your dd doesn't have seizures... I'm not convinced! Seizures can be such a very very random thing - my dd's seizures did not happen often - there was no way we could have predicted when to have her set up to be running an eeg to catch one simply because of the randomness of it. However, our neurologist walked us through a very detailed history with a ton of questions about dd's history from the first day she came into our lives, and was able to draw out specifics that we would never have related to seizures and pull together details into a picture that made it clear she'd had seizures. Then... when we had a follow-up appointment with her *real* neurologist (neurologist #1 who made the diagnosis was a colleague who was taking calls while the real n-dude was on vacation)... the real neurologist had a clear eeg, was in a hurry, and couldn't be bothered. The same thing has happened with our same dd with other medical professionals when she doesn't fit an easy-to-diagnose pattern. Really really frustrating! But it doesn't make the symptoms disappear... just because they are difficult to make sense of and don't fit what is "typical". Sorry, I'm getting off track - basically just wanted to say, hang in there, keep a list of what you do observe, and just because a person is a professional, don't doubt what you feel is going on either. You're the person who is living with your dd and knows her best.
My apologies for rambling - I hope some of it helps.
polarbear
