J.L.
There are these neckerchiefs they sell that have something in them that stays cool, you put them in cold water first to activate them and then wear them... Perhaps there is a way to hide it under her uniform or maybe they sell smaller ones that are more like patches. I googled and found them online awhile back. The key is that they are on the back of the neck, there is a spot back there that really helps with cooling the body down.