Again, not trying to debunk you. I'm just curious.
Observations of her diet and symptoms. 2 main qualities being observed here. 1 is migraine/headaches, the other is confusion. Both seem to have a 1-2 day delay, e.g. eating a very triggering food then in usually 1 1/2 days she will have migraine/headache, likewise increased confusion. So the trigger foods originally had been observed to be dairy mainly, but we had come to realize many foods were also triggering it in a lower-grade dairy was just very noticeable. So for your hypothesis of it being exogenous carbohydrates, which is a fair hypothesis, for me the fact that dairy is such a trigger makes me think it's not the carbs so much as the whatever is feeding the candida. So basically one of the reasons I believe it's the candida is because observationally, the foods in her diet that caused migraine/headache/confusion lined up with the foods that fed candida. Then going on anti-candida diet we don't have any of those symptoms. Yes it could still be something else. Anti-candida diet is as you say, low-carbs and low sugar which is good for many things. The dairy part though, in particular, leads me to believe it's more than carbs.
Then there's the lab testing that shows in particular indications of a severe yeast infection in the gut, e.g. candida.
So taken together, I'm led to believe candida is the main thing affecting her, though I'm very open to it being something related and not candida as such, but still all evidence so far points to candida.