I have been scouring the web trying to figure out what to do. I am wondering if this may be canker, but it doesn't have a yellowish cheesy look to it. I want to see first if there is a simple treatment, and if necessary take her to the vet. Unfortunately, it is Memorial Day Weekend, so it might have to wait for a few days.
She is still eating, but can't eat any pellets, they need to be ground. Her poop is watery as she hasn't been eating too much.