Why would my dog suddenly refuse to chew her food?

My dog suddenly started spitting out her food and treats after chewing a couple of times so I assumed she had a tooth problem and that it was too painful to chew. I fed her wet food until I could get her to the vet and she seemed to be able to get that down. I brought her to the vet yesterday and they said she could use a cleaning but that her teeth and gums are perfectly fine. They sent us home with pain meds and instructed me to give her a pill about an hour before feeding her.

I followed my vet's instructions and my dog still had the same reaction when I put the dry food in front of her. After she realized that she wasn't getting any wet food, she just started swallowing the little kibble bits whole, I assume because she was so hungry. I called my vet back and they instructed me to give her another pain pill before bed, one this morning and try feeding her again today when I get home. If she still doesn't chew they want me to call back.

I should also note that my dog is 7 years old and has NEVER turned down her food or treats. I can tell something is wrong. I trust that my vet is doing everything she can for my dog, I just wanted to see if anyone had any suggestions of things I could bring up with her, because I have a feeling we'll be going back. Thanks!