I am on a FB group for people who have dogs with yeast infections, and they promote (require to be in the group) raw feeding. And they are very strict that there should be NO fruits/veggies/grains at all, as all three of those things feed yeast. So that part I have heard before, and would say that could very well be true. Probably it would take longer than three weeks though to see a difference, when you remove those things from the diet. As for the protein being hard on her, the protein in raw is very different than the protein in a kibble diet. Not the same thing at all, and your vet might not realize that, they don't get much training in nutrition. This would not even be a flag on my radar, I plan on feeding prey model raw to my dogs for the rest of their lives. Bacteria in raw meat does not feed cancer. The only way this might be a concern, would be that a compromised immune system from cancer and chemo might make the dog more susceptible to bacteria. If (god forbid) one of my dogs is ever diagnosed with cancer, I will look into it more and would switch to homecooked if necessary. But just being a senior dog in general is NOT reason to stop raw.