It is a really messy option but have you tried Gentian Violet? That stuff was a serious miracle cure for my son and I. I applied it to my nipples once in the morning, once at night for two days. I would also take a q-tip soaked in the GV and swish it in DS mouth at night, just for those 2 nights and we kicked it!! (Though since you are already treating DD with a RX you wouldn't have to treat her I suppose).
If you talk to a lactation consultant a lot of them may say that it is an old remedy and not really used anymore and will recommend a prescription. However, if you talk to Le Leche League leader or any of the amish they will tell you to use the Gentian Violet. None of the pharmacies I called carried it but they ordered it and it came in the next day. It was like a 4 oz. bottle for $6. Well worth the money! I kind of doubted that some natural remedy like this would really kick it as I was in EXTREME pain but it was just amazing! I did have some residual tenderness for a couple weeks while everything healed up but it kicked the thrush so quickly!
Here is some info on it:
http://www.breastfeedingonline.com/6pdf.pdf
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