He took one look and knew it was a type of yeast infection - basically, it starts as slight diaper rash
but develops into a larger rash
that doesn't respond to typical treatment. She was prescribed econozole - however, many actually get relief from over-the-counter topical creams (apply to the skin where the rash is) for yeast infection. Perhaps your daughter's doctor, pharmacist, or nurse could advise you over the phone if it's worth trying.