Adopted cat was only fed Temptations

Hi all,

My grandmother is very ill and I took her cat home with me today, as I don't think she will be coming home to take care of her :(

She is a 3 year old, spayed, tortoise shell cat. She is very docile and sweet. The thing is... I discovered that my grandma has only been feeding her Temptations treats (as food, in a bowl) and squeezing out 2 Churu sticks onto a plate every day. Obviously, this is NOT ideal and I am looking to get her real food ASAP (also a vet visit).

I am just looking for advice on what food to get for her, as I don't want to upset her stomach. Brands, opinions on whether she should have dry AND wet or just one or the other.

I have a cat already but he is on a prescription diet. I'd also take advice on how to feed separately and keep them out of each other's food. I've never had two animals living together 😅

TIA! <3