I've investigated gular edema as thoroughly as I can without actually being in a lab setting and running blood vitamin levels. There is limited information on it and still a lot of unknown. While it is typically gular edema there is a small chance it could be infection of the more cranial air sac projections of the lungs found in that location. Usually accompanied by respiratory signs. And some females get transient edema only when they're gravid - you're sure she's not gravid? With gular edema fat soluble vitamins like A and D are the most likely culprits by far based on my experience. Just like with people with edema there is a concern for liver or kidney dysfunction causing fluid imbalance but in the ones I've done bloodwork on there were no abnormalities to correlate it with organ dysfunction. Vitamin D chronic overdose can cause damage to the kidneys, which is well documented in iguanas.
I believe mine were caused by vitamin A in the several chams I've had get it. It was transient in mine after the inadvertent addition of high levels of vitamin A (trying to use up extra parrot pellets), however as you know correlation does not necessarily equal causation. There is an ongoing debate on whether or not chameleons can utilize beta carotene and other VitA precursors, or if they need preformed vit A. It's still an unknown.
Regardless, the most success that I and several others have had is lots of natural sunlight, keeping them very well hydrated to help flush everything out faster, continuing high calcium/low phosphorus supplementation to support good kidney health, and stop any multivitamin supplementation for several months. If you are gutloading well then you do not have to worry about nutritional deficits from not using a multivitamin. After a few weeks two of mine's edema cleared up and for the worst one of mine it took nearly 6 months and it came back a few times but not as severe. He now has gout so even though his kidney values are still normal I do suspect some kidney problems that could have caused the edema a few years ago. Won't know until he passes on and I do a necropsy with histopath but that's my speculation. Carol had a cham that came to her with severe edema and his never went away despite the same approach I took. He happened to have gout at the end as well. There is still much to learn...
As long as she is acting fine and it does not seem to be bothering her I wouldn't worry too much about fluctuations because that is kind of par for the course with edema it seems. There is really no way to reduce quickly it short of having it drained by a vet, but it will fill back up again and sometimes within 24 hours. I've tried it.
