That kitty is in bad shape. Stress hormones are making her not eat.*
Just do everything you can. I would even avoid getting upset around them, they need as little stress as possible if you want them to eat. Kitties bond to a protective figure, she’ll be more calm if you try to be.
Cats live a small part of our lives, but we’re there for all of theirs.
She is young enough to turn around. The scar tissue on the kidneys don’t disappear, but the rest of the kidney slowly regenerates (multiple tissue types thought to not have stem cells actually do have some)
Your kitty would like a small dark place that’s warm, or to be in your proximity. Safer she feels, the more likely she will eat and get meaningful sleep. Humans don’t like small places, but it makes cats feel safe.
*We can see that things like adrenaline will raise blood sugar. Unfortunately her blood sugar might still be low. Stress hormones still interfere with hunger hormones, regardless of blood sugar.
We got rest/digest which is a building state fight/flight/freeze is a state in which the body breaks itself down for energy. She needs to be in the first bracket of states, the second one will continue to stress her kidneys.
You also can’t force her to live, remaining calm will be her best chance. Even if she is fucked just be with her and stay calm.