J.P.
You should always check with a pediatrician, but you may want to try these things first to see if any work, first (if you're trying to save a trip and $$ to the doctor).
Don't use any bubble bath or adult soaps on your daughter when bathing. Try to use soaps that are hypoallergenic/ all-natural. Also, if she's wearing undies, make sure they are cotton and that you're using perfume-free detergent. She may have to have non-perfumed wipes to use to keep clean between wiping (little girls don't always wipe really well and the left-over urine can also irritate and make it itchy).
My daughter had a problem with yeast as a baby and my pediatrician said that I could use a small/thin amount of Lotramin anti fungal(or Gynolotramin)on her bottom. It worked wonderfully, but I wanted to find what kept causing her to get yeasty. I found that certain diapers were the culprit and wouldn't let her skin breathe, and then had to switch diaper brands...so if your daughter is using diapers or pull-ups, you may want to try something new, or try the Lotramin. Your doctor may have another suggestion and you won't have to go in for an appointment, since its really a common issue with little girls with sensitive skin. Its always a good idea to call and check first. Hope that helps, and good luck!