This probably is a yeast infection. It is almost impossible to avoid systemic yeast overload following a course of antibiotics. My doctor always recommends that I take about a tablespoon probiotic yogurt with each dose of antibiotics, and then continue with daily servings of the yogurt for a month of so after I've taken the last dose. She recomends this for her pediatric patients as well. The active cultures in the yogurt counteract the effects of the antibiotics, keeping a good balance of healthy bacteria in the digestive system.
Foods that contribute to yeast overload and should be avoided at all costs are: dairy, wheat, and sugar. I don't eat any of those any more, and my health has improved like you wouldn't believe! I use honey or maple syrup in place of sugar (at the recommendation of my doctor), and avocado in place of cheese, since it has a similar texture and tastes so good. ;-) The only grain I eat is oats, using oat flour when necessary, although I just go without bread, opting for sandwiches in the form of salads now.
Good luck getting your daughter's condition cleared up!