I had two kidney cats. One was caught at 12 years & managed with Sub. Q fluids & diet for 2 years. The other went downhill in two months. You could do the fluids at home, the vet could show you how. The determination I made was when the cat started throwing up it was more then once a day but not yet chronic.Throwing up is part of kidney disease you just have to know how much is too much. The cat that lasted 2 years was force fed a few times & came back around. They can rally for awhile, it depends on how much you can give fluids & blood tests. The end result unfortunately is the same. If you choose to hospitalize her, your vet will know in 2/3 days if any improvement, & you can carry on with it at home. It's really what you can tolerate. Trust your bond & her signals. Even if kitty rallies for a few weeks it can give you time together. Make the decision for the both of you.