Thanks for your question, I am Dr Asanghanwa, your daughter might have an aphtous condition which is an inflammation of the buccal mucosa following an infection. This is generally due to Herpes Simplex virus in most cases. The soreness of the buccal mucosa goes away as the infection resolves and your daughter is already on antibiotics. It will be a couple of days again before the soreness goes away. However i would advise on frequent mouth washes with Hextril solution, or Bicarbonate solution every six hours. Continue with the antibiotics and add a Paracetamol sirop dose for weight measurement four times daily and consult your physician if the fever persists. Good luck