What is the best food that you can feed a diabetic cat?

This cat is a spayed female, 9 yrs old, and also overweight. She is on special cat food from the vet. She was recently put on insulin 2x a day, instead of once. She is not losing any weight, even though she is restricted in her eating. She does not like the canned food that my sister got from the vet, so she is eating the dry(I think it is OD) Is there any other food recommended for a diabetic cat?