May be systemic. A lot of possibilities. How long has this been happening? There are systemic syndromes that can do this. How old is she? The age could be related to the diagnosis. The sore could be apthous ulcers. But are they painful? If they are not this could it could be a variety of viral syndromes. You need to MAP the fever curve. She would benefit from seeing her physician.
Sores in mouth. How old is your daughter? Young children often get an infection called acute herpetic gingivostomatitis. This is an infection caused by the cold virus. They also get an infection called hand foot mouth disease, which is also caused by a virus. Both last from 10-14 days. See your children's dentist or pediatrician for a diagnosis and treatment.