I would make sure that you are doing annual bloodwork (chemistry panel and cbc), and urinalysis, to know what her normals are, and to watch if anything is changing over time. If you see changes, I would run the bloodwork more frequently as I made changes.
I'm a fan of a high meat and veggie homecooked diet, maybe put together by someone like Monica Segal or Sabine Contreras (nutritionists), and I believe that that is also good for diabetes. At the very minimum, I would want foods low on the glycemic index. Off the top of my head, those are the first things I would look into.