Hi Kathy and extra sweet Shanty!! Welcome to the FDMB...the best place to be to help your kitty!
First, the dry w/d is too high in carbs (and very expensive too!). There's no reason you need to buy an expensive prescription diet. A lot of us feed Fancy Feast Classics or Friskies Pates from WalMart.
You'll want to get wet foods that are less than 10% carbs. This chart shows pretty much every food available and the percentage of carbs (column C)
Dr. Pierson's Food Chart
Since you are giving insulin, don't transition too fast though. Shanty's blood sugar could come down too fast!
The next thing you'll want to do is learn how to home test. We can help teach you how to do this, and you'll get much better results (as well as more accurate ones) by testing at home. Just the trip to the vet can raise the stress levels in your cat, which can raise the blood glucose levels as much as 200 points! It's also a lot cheaper than monthly curves at the vet!
WalMart carries Relion Prime or Confirm blood glucose meters in the pharmacy. The meters are about $15, and the strips for the Prime are $9 for 50....for the Confirm they're about $18 for 50 (the Confirm takes the smallest size blood sample) Don't let your vet convince you that you must use a "pet only" meter. The majority of us use the Relion and do just fine without paying $100 for a meter, and over $1 per test strip!
The members here have thousands of hours of experience dealing with the day to day management of diabetes and we can help guide you along the way. I think most of us only see the vets now for routine care, like shots and checkups
Edited to add...I do know of Banfield..they have a pretty good reputation, but there aren't any "feline diabetes experts" that I know of. Vets can't keep on top of the latest treatments for every disease, every animal they see...and a lot of them get their "nutritional education" from maybe one class in vet school...and then the only continued education they get is from high pressure salesmen trying to sell more of their products. The members here live and breathe feline diabetes. I seriously doubt if there's anything they haven't seen before..and figured out how to handle!