hi..Thanks for your query.
From what you describe ,there can be two possibilities:
1) Infection : is the area is warm ,tender and red ,there is a possibility of an infection in the cheeks.Treatment would include antibiotics ,warm compresses and anti inflammatory medication.
: Due to contact with external allergen or air borne allergens ,she might be having an allergic dermatitis
.Treatment includes mild topical steroids
and anti- histaminics.
I would suggest you to visit your dermatologist
for an appropriate management.
Hope this is helpful..Best wishes!