I'm sorry about your kitty, brgurgogrogigrgiflil. At least she has enough of an appetite to eat Purina garbage and roast beef. Hoping the bloodwork has been steady and that she's feeling comfortable. Enjoy the cat snuggles.
Yeah, at the emergency hospital, we used to use kitten/puppy food to entice patients that weren't eating. And in both places I've worked, we'd try baby food as well, usually the meat based ones. You can also try warming food up in the microwave a little bit first. Sometimes the extra heat makes it smellier and that extra smelliness can help overcome some nausea. It's tough to balance all of these things. The kidney formula is ideal but it's not all that appetizing even to a lot of the healthier cats, so if your vet thinks you may be at the point where getting calories in her is more important, then it's worth taking out the roast beef and other stuff.
Is it possible to mix in some of the kidney food with the smelly food so at least he gets some of it?