B.W.
Are you breastfeeding? If you are and she has thrush or a yeast infection then you need to be treated as well.
BAbies very easily get yeast infections, which breed in warm moist environments, like a diaper. ANd she was just on antibiotics which can easily cause it. I would get some acidophilus, break open a capsule and get some powder on your finger and let her suck it off, that will help get some good bacteria back in her system, and call your doctor, who will probably tell you to use lotrimin or another antifungal on her privates to clear it up.