Children with scarlet fever
present with characteristic clinical features like sore throat
, cough, fever with erythematous rashes (sand paper like) over the body including face, strawberry tounge and cracked sore lips. Localised reddened raised lesion with suspected pus inside indicates some cellulitis
(mastitis),which is different fromthe usual rash of scarlet fever. Although she is getting antibiotic, a clinical evaluation is needed to exclude any abscess which may need incision and drainage
So I would suggest you to consult your doctor for examination and to rule out evolving abscess.