Well, we started off with adding wheat to her diet successfully, I thought. Then I had a couple of days where I wasn't 100% positive. Then I had a couple of days where I caught myself thinking, "Maybe she's just tired," or "Maybe her blood sugar is getting a little low." So we decided to go off wheat and see what happens. Lo and behold she was a darling child again. It's bizarre - she really doesn't have horrible behavior per se, it's just when you take her off wheat it is VERY noticeable how different she is!
So no wheat for now. But wait, there's more...we started tree nuts at the same time as wheat so it could be that instead. I have a book that goes in depth into elimination diets, and even breaks it out to single food elimination diets versus multiple food elimination diets versus rotation diets (whatever that is). So I will read up on that and then try wheat and tree nuts separately.