The vet won't be open unless it's an emergency vet. Have you noticed liquid around her mouth again? Has she fed recently? I've seen monty open her mouth and "yawn" a few times. I took her to the vet, concerned, and paid $600 to find out that she was just readjusting her jaw. Does one side of her mouth go down further when she jerks it down? What kind of substrate do you have in your tank?