She must be having fungal infection which we call tinea. The treatment for fungal infection is simple. You have to take anti fungal tablets and creams for 4 to 6 weeks following which it resolves. Do not apply soap on that area and do not self treat with over the counter steroid creams. Mistreatment with steroid creams and self treatment with cheaper generic medicine is the most common reason for recurrent disease. Kindly send photos using online consult option for accurate diagnosis and treatment.  If this is fungal infection, it needs to be treated as early as possible as it will spread further on your body  and also to other people in the household.