Very few people here feed prescription foods. There is really nothing "prescription" about them, except the cost. A vet has great food info here:
www.catinfo.org. She also has a food chart so you can compare the carb counts of different brands. We suggest staying 8% and under.
I feed Fancy Feast and Friskies. It's what I can afford and I figure since cats would be happily eating a mouse in the wild, byproducts are not a big deal.
She probably want you to buy the AlphaTrak. It is a pet meter. There is nothing wrong with it except the cost. Not only is the meter expensive, but the strips are what you need to buy often, and they are very expensive. Human meters do read lower than the pet meter, but since we are looking for trends and patterns, we don't see it as a big deal. The least expensive is the ReliOn from Walmart with the whole set up being around $40.
If you really like your vet, and money is not an issue, you could use the pet meter. As far as the food goes, she isn't there when you feed your kitty. It's your choice. It's usually a balance between doing what is best for your wallet and your cat and keeping your vet. My vet wanted me to feed prescription foods. I took a small bag and started feeding Fancy Feast. When his numbers started to drop, I just told her he wouldn't eat the vet food. She didn't argue as he was doing so well; we decided to agree to disagree.
I do some reading, check how people are doing here with the protocol of wet low carb and decide what you think is best for your cat.
We put together a protocol for ProZinc; it is in blue in my signature.