It sounds to me like it is a yeast infection. Get some Nystatin cream or powder from the doc and she should be fine. I am a med-surge nurse and have many women and a few men that have the same symptoms. Under the breasts is prime place for yeast to grow especially when it is hot outside. Hope this eases your concerns.
oh thanks...sorry I don't know what's yeast is it any harm ?
Very informative article if you are not aware of what causes and symptoms are:
Hope you find this helpful!