T.S.
Bubble bath and/or soap in her bath water is a likely culprit. If she's taking baths it would be a good idea to switch to showers at this point. If she already takes showers, make sure she's washing herself from front to back and doing so early in her shower... (rather than at the end of her shower with the washcloth that's picked up everything from the rest of her body).
Poor baby.
Lastly... Whether she likes it or not... try to get her to drink a glass or cranberry juice every day. (not cranberry cocktail but the real juice). If really can't stand it, you can get cranberry tablets she can take each day to help keep her little pH in order.
Good luck.