Hello Jennifer and thanks for your query
As per your mail your daughter is suffering from oral infection and for this she is on antibiotic since than. You are taking a good antibiotic but with this you have to take a proper oral care of the mouth. Do Betadine
gargles mixed with lukewarm water every hourly, take multivitamins and vit. C for early recovery. You can apply a local gel on the blisters for pain relief, it will also help in healing.
When you get a sort of relief you can start take orally but not spice. Do regular gargles after every meal.
Hope this will help you.