If she is eating well, that is good. I would ask about the fluids at your normal vet the whole setup cost me about $20 when my cat had DKA. Usually you do them once a day for a couple days, and one bag will last a few days. If you can, keep track of the time you gave the insulin and times you took the blood sugars and results, and list them here. This will help people here better understand what is happening with the blood sugars.
How much insulin are you currently giving? If you take blood sugar before the shot, then 3 hours, then 8 hours, then before the next shot and they are all above 300, then you should raise the insulin by 0.5 units and keep that dose for at least 4 shots. Since she still has a small amount of ketones, it means she's not getting quite enough food and insulin. Don't worry if the dry food raises the numbers for now, you can always adjust the insulin. She needs the food.