Hard food substitute for diabetic cat? Food recommendations?

Does anyone have any recommendations for a good substitute of replacing hard food for cats? Truffles has been diabetic for 2 years now and never gets hard food anymore, she only eats Fancy Feast pate and gets freeze dried treats. However she has had terrible diarrhea these past 2 years from only mainly eating wet food. I have tried probiotics/pumpkin purée, the probiotics didn’t do much and she wouldn’t eat the pumpkin. I feel like since she doesn’t really eat any solids that it gives her such bad diarrhea I feel terrible for her. She is a long haired cat so you can imagine how great that combo is together. I have tried the special diabetic hard food for cats but it spiked her blood sugar just as bad as normal hard food would. I’m looking into the instinct freeze dried adult cat food now and I think we are gonna try that. I have spoken to her vet about it but she says there’s not much I can do. Is it an insulin issue? I check her numbers 3x a day and sometimes have a glucose monitor on her so it can’t be high glucose levels. I just want to help my baby as much as I can! Diabetes sucks!