I feel your pain! My daughter just got over one about a month ago - she was 22 months. The doctor gave us three refills and we used ALL of the Nystatin. It took just over 2 weeks to completely go away. Unfortunately, I think what helped her the most was that I had her naked about 75% of the day.
As soon as she woke up, we wiped her down and had her naked through lunch. Diaper on for nap, diaper off after. We gave her a bath every night (some nights no soap) and let her be naked for about half an hour after her bath to get completely dry before putting a diaper on for bed.
Also, avoid sugar as much as possible and give her yogurt EVERY DAY! I gave my daughter plain yogurt with probiotics. It's a little tangy, but I mixed in banana and a bit of cinnamon and she was all about it! Avoid juice completely for awhile and cut down on fruit. The sugar breeds the yeast.
Good luck!