Is it possible that she is reacting to some kind of t.p., laundry product, soap, bubble bath etc? Maybe even the cleaner you use to clean the bathtub or her bath toys? Keep in mind that a lot of soaps, laundry products, & cleaners don't rinse off/out completely. Even VERY SHORT or VERY DILUTED contact can set off a reaction if you are sensitive. My DD & I both have chemical sensitivities & I have to watch all of the above or we get a reaction that seems like a yeast infection.(which I have also had) Many brands of t.p. drive me up the wall, same w/most soaps. I buy most of our clothes (except underwear & socks) at the thrift store but I have to wash them repeatedly to get the residues out of them or we will get a really bad irritation that seems like a yeast infection- even though we are wearing underwear- the residue migrates through the underwear. New clothes are the same way because of the finishes they put on new clothes. Even sitting on the bed while undressed if the sheets have residues. This can happen even when items are washed out enough that it doesn't bother us in any other way. There is NO WAY I could ever use reg. bleach on clothes-I would never be able to get enough out to be able to wear it. Having a yeast overgrowth will make the skin MUCH more sensitive. Maybe this isn't the case w/your DD but it may be something you want to look into.
Along the same line, we use all natural fibers for clothes, sheets, blankets, futons, etc. Synthetic fibers cause us problems including rashes, insomnia, & just in general run down your health. All items outgas which means that the molecules that it is made of get into the air around it. Outgassing is why cars have that new car smell & why a lot of plastics have an odor. When synthetic items of all types outgas, it can cause illness. Synthetic fibers are basically plastic and are heavily coated with formaldehyde- it's the formaldehyde that makes fabric perm. press (including wrinkle-free cotton). Sheets get coated the heaviest. Something you might want to look into.
I also have chronic yeast/fungal overgrowth. Check out Doug Kaufmann's Fungus Link books. Also the website www.knowthecause.com
. Find out if the show Know the Cause is available in your area & if it is watch it. There are a lot of very good threads on this site about fighting yeast.