A chelitis, possibly related to photo-sensitivity.
I'm sorry, I meant Theraneem mouthwash. They also make toothpaste.
Try changing her toothpaste. Jason's makes toothpaste that is good for people that start reacting to certain ingredients, but some people find that just one brand, such as Crest, is the culprit.
If that doesn't help, try having her swish with Theraneem toothpaste. It has natural ingredients that fight bacteria and yeast without harsh ingredients. It is pleasant tasting and doesn't burn. Still make sure she spits it out after swishing.