Not every UTI will turn into a kidney infection, but there is a higher potential for it to happen in a CRF kitty.
Sierra's doesn't progress that far.
I would say at this point give her whatever she will eat, if she's feeling that poorly
give her anything to get her tempted to eat. You could try a little parmesan cheese sprinkled on her food, or some treats like PureBites Freeze Dried Treats
, or a tiny dab of melted butter, a teensy pinch of catnip, shredded bits of deli meat etc just enough of something to peak her interest.
You can always discuss Phosphorus binders with the vet if Sierra has high blood phosphorus levels & will not eat something with a lower phos range.
Force feeding might also be an avenue that might need to be looked at.
man that's tiny she sure doesn't have any room to loose. Can you put boxes/stools infront of the couch/bed/fave places to give her "steps" to get up to where she is comfortable? For Duffy I had a sturdy cardboard box & a rubbermaid tote beside the bed so she didn't have to jump up, just step up & then up to the bed.
Are you able to place a phone book or such of a similar thickness under the food/water dishes? I found that helped a lot in reducing nausea, also makes it easier on the neck reaching the bowl.
Sierrra is likely also feeling pretty low because of the infection
for kicking that asap
It sounds like fluids would be very beneficial to start soon, the increased hydration makes them feel better, plus it flushes out more toxins from the body which will make them feel better as well. Giving sub q fluids to your own cat is honestly not as bad as it seems at first. Some good tips on it here: http://www.weirdstuffwemake.com/weir.../catjuice.html