Diabetic Cat?

My cat has been diagnosed with early onset diabetes. So although she is not insulin dependent yet, she could be. I am doing what I can to try to prevent this from happening. Her diet has been changed to solely Hill's m/d feline biscuits. I am diabetic myself and this is the part I struggle with. The vets have told me she is to have nothing else to eat ever. What harm can her having a bit of fresh meat do from time to time? Surely it can't raise her glucose levels? So long as she is still eating the biscuits as well, what could be the problem? I'm afraid she will get sick of her biscuits, and then what will I do? Please any help would be appretiated. I don't want her to get bored with her diet, I would like to mix it up a bit but in a healthy way.