K.M.
I have a 2 1/2 year old who reguarly gets yeast infectiona and has done so since she was 15 months old. She started getting them as a reaction to antibiotics she was allergic to and now reguarly gets them. When ever she sart complaiing about being sore or itchy or strts scratching her vagina or when I notice that is it very red I give her children's powdered probiotics. Initially she could tell if I sprinkled them over her cereal so she would get this special treat of some juice (she ever gets juice to drink - just water) and I would mix them into a small amount of juice and give it to her in a toy tea cup - which she thought was a special treat!!
Probiotics cannot harm her and I have found they help with a variety of problems - yeast infections, keeping her regular when she may not have been for a few days, warding off a cold (amazing what they can affect).
Anyway you probably do want to have her looked at but in the meantime I definately woud suggest probiotics.
Good luck.