"Insulin is a
hormone made by one of the body's organs called the pancreas. Insulin helps your body turn blood sugar (glucose) into energy. It also helps your body store it in your muscles, fat cells, and liver to use later, when your body needs it. After you eat, your blood sugar (glucose) rises."
With cats, they do better with dosing twice a day, 12 hours apart because they metabolize about three times faster than people.
Vetsulin is an in-and-out insulin so it should not have any accumulating effect. If it looks like that, it may be Kitty's pancreas spurrting and doing a little work
I think she needs the PM shot, even if it's less then 0.25U. You hold the syringe though