The two other people are not vets. Phone your vet and remind her of the sodium concern you have. Ask what food you can use.

I have yet to hear about a high-quality food CAUSING crystals.

There are several brands of "vet" cat food - Hills, Royal Canin, and maybe one or two others.

The vet is the only one that can "tell" you about Hills, and the others, because there are different kinds within each brand for different conditions.

Or even go in to your vet's, and have one of the techs show you all the cat foods, and what they are for.