I wouldn't think that "chapped and peeling" is a yeast infection. Yeast infections tend to be more along the lines of red, swollen, glossy (from skin excretions) and possibly bleeding. Since it's gone on for so long now, I would take her to the doctor and they can run a combination test for yeast and for strep (which manifests as a diaper rash in babies, I know, weird). In the meantime, you could always try to put desitin on it and reapply every time you change her diaper, or you could try breastmilk. You just dribble a little on, pat it around for coverage and let dry. It forms a barrier on the skin that is sticky to the touch, but protective and it also has lots of good fats in it that can soak in and help heal like a lotion would. Believe it or not and pediatric nurse told me about this with my first son and it worked like a charm. My second son wasn't so lucky. I learned that breastmilk should not be put on a yeast infection rash because of the high sugar content; it just feeds the yeast and makes the rash worse.
If your doctor says it's yeast or strep (my little one had a rash that was both) then ask for a prescription for Greer's Goo. My little one struggled for months with diaper rashes that wouldn't seem to clear up until we tried this medicine. One week later, he was rash free and has remained rash free for several months now.
Best of luck!