Hi, well, my situation isn't diabetic v. non diabetic, but, I do feed one boy food that the other six don't eat. For the most part, it works VERY well....I feed Tex on the counter, only. I do not encourage other cats up there,and he doesn't eat their food which is on the floor. Now, Allie and Georgia sometimes sneak a peek in Tex's food dish, but, run when they see me....I just talk harshly.

I would give my situation a 89% success rate in keeping other's from eating Tex's food, and 100% in Tex not eating their food (which is more important).

Good luck, and special thoughts for your friend thinking of adopting a special needs kitty. She is to be commended.