Hello and thank you for asking your question on just answer. My name isXXXXX will try to help.
How much does Annie weigh?
Is she currently taking any other medications?
If she is already on metacam, she can not take aspirin or any other pain medications. The metacam is for pain so give her a dose of that.
If you know which tooth is hurting her, you can rub "baby oragel" on the gum, surrounding the tooth, with a q-tip. It is a topical anesthetic used to numb the gums for teething infants. You can apply a little every few hours. They sell the baby oragel in the infant care section of the drug store.
You can soften her food with warm water or warm low sodium chicken broth.
If you think she is in a great deal of pain, and the metacam is not helping, You can take her to the emergency clinic where they can give her a stronger pain medication that is similar to "codiene." If she is still able to eat and drink, she can probably wait and see her regular vet in the morning.
I hope this helps.