She might have worms and you need to get her some dewormer meds and it will tell you how much and how often to give it to her. But I would call the vet and see if they can see her. If the dewormer don't work. But don't wait to long it cold be something more dangerous. She might need to be screened again for cancer as this can develop quick. Good luck
Worms are very, very unlikely in a dog this age and should not cause anorexia without signs of diarrhea. My top rule outs in a sick older dog include kidney disease, liver disease, diabetes, and cancer. Whether this is a new type of cancer or if there were microscopic metastasis that are now causing a problem. In older pets dietary indiscretion (eating garbage or weird things in the yard) can produce longer periods of gastrointestinal upset than in younger dogs. They just don't bounce back as quickly. Any pet that stops eating and drinking is at great risk for secondary dehydration that makes them feel even worse. Your dog needs to be examined by a veterinarian to rule out serious causes of anorexia and receive appropriate treatment.
