I'm going to be somewhat more moderate. The issue is largely one of the carbohydrate content of day food. If I recall, you were feeding a dry food that was exceptionally high in carbs (i.e., Indoor Weight and Hairball Control = 40% carb). If you were to feed a canned food that was 40% carb, numbers would be off the charts, as well. In addition, the ingredients include: Chicken By-Product Meal,
Corn Meal, Corn Grits, Ground Whole Grain Sorghum, Dried Beet Pulp, Powdered Cellulose, Chicken, Chicken Fat (preserved with mixed Tocopherols, a source of Vitamin E), Dried Egg Product, Natural Flavor,
Brewers Dried Yeast, etc.
The items that I put in bold are plant-based. Cats are obligate carnivores. What that means is that they do not need vegetables and grains in their diet. In fact, they can't digest those products. They need protein. In fact, they need muscle meat, not "animal by-products." The dry food you were giving Lucy fundamentally did not meet her nutritional needs. Dr. Lisa's website goes into great detail about the myths regarding dry food. There are any number of cats we've seen here that once they were transitioned onto a low carb, canned food diet, their diabetes was history. It was the dry food that was causing the diabetes.
Unfortunately, neither vets nor MDs get a great deal of training in nutrition. Vets get the bulk of their information from the sales reps from the major pet food companies who sell them prescription foods to resell to us. As a result, most vets believe what they are telling us about the nutritional basis of the dry and canned foods they are selling at a profit. Unfortunately, these prescription foods are not made with quality ingredients. It's problematic that some of the diabetic dry food diets are very high in carbs.
There are a handful of dry foods that have low or no carbs. If you are determined to feed Lucy dry food, I'd encourage you to look at
Young Again as an alternative. Canned food will still be better but at least this is a food that is ostensibly zero carbs. There has been one person who fed Young Again and their cat did well.