How about treating it the way we treat yeasty bottoms in babies
  with  thrush.?
 I've used gentian violet on babies bottoms......sparingly
 so....approach with caution.   Also, and this is anectodal,  baking
 soda in cool water swabbed over the area seems to help.  Wash the
 bra often (cotton if she can pick)  air dry the area under the
breasts, like we would with a sore bottom, The usual changes to the
diet.... plus adding acidophilus..and if all else fails, how about a
cream for vaginal yeast applied to the area?  (say miconazole
perhaps) That's the best I could do...hope it works.

 Stephanie Pearl IBCLC
>