This will be 2 part and somewhat long winded - I apologize in advance.
I'm not sure how old she is, but if your vet is willing to teach you, you can get a bag of fluids and help her kidneys perform better with doing sub-q fluids. Most vets don't offer to teach their patients because most won't ask. But I say ask. When I asked they had me bring in a calm cat (but your sick kitty would do) and its far easier than pilling ANY cat. Assuming you're not horribly squeamish of needles. If our vet tries to charge you more than $20 for a bag of fluid and some needles - ask around at other vets in the area. My vet charges $6 per bag of fluids and I can get the syringes from them for $5 for 10 - 28g needles or I can get the same amount for $1.99 at the farm store up the road. So its not as expensive as most will make it out to be. Even if you can get them to write a script for it, you can order it online from 1800petmeds or jefferspet (i think) and others for around $12 or so shipped. It can be stored in your kitchen cabinet, doesn't need to be refrigerated or really special handled other than an alcohol swab to the port when you draw fluid. But really that was it.
My last cat - prior to adopting Biggie in NY and then moving to IN where I now have uh 32 inside and an alternating colony outside of 14-21 - depending on weather. (In winter we get around 20-21 every day, in warmer weather there are more farm cats who are well fed so we don't see as many in summer), but Darla, the pain in the ass that she was - I'd rescued her from the SPCA in Rochester NY in 2001, she moved with the ex and I and a dog back to the area I grew up in. Darla was always super healthy, then one day she wasn't. I called the vet as soon as she started running a fever. That was a Thursday. The vet was out and the office told me to call in the next morning. Friday AM the Darla's fever was very high, and she was panting. I called the vet back. I knew something was WRONG. They told me "its just the URI going around," I said this is NOT a URI, she's got a very high fever and she's panting. They refused to see me and at the time it was the only vet within a 75 mile one way drive. I couldn't afford vet appt and gas $ to go to an emergency vet 120 miles away. They scheduled an appointment for Monday. I took her in for them opening Monday morning - 6 hours early for her appt. I take her in and show them the dying cat. The vet takes us to an exam room and tells me I've CLEARLY abused and neglected the cat by failing to bring her in when she started showing signs months ago (he'd just seen her not even 2 weeks prior to that and said she was fine). This vet had a history among friends "he's the only vet in the area and he repeatedly refuses to see animals when they're sick and rather insists you wait to be seen only then its too late, and its always with cats." In NY I can record a conversation without the other party knowing as long as one party consents to the taping - since I did it, I consented. I had recorded his nurse telling me on Thursday he wasn't in and to call on Friday, and I recorded the Friday call(s) and the insistence by them it was nothing to worry about and THEM telling me I'd get in on Monday. Darla was put to sleep on Monday morning to ease her suffering from acute multi-organ failure that a necropsy I insisted on and paid for out of pocket said could have been treated and her life made far less miserable than it was during the 72hrs of delay by the vet.
My recording, was proof enough that I wasn't at fault - the vet tried to have me charged with animal cruelty - except the local cops who came to the office, looked at me, knew me and my family and said there wasn't enough evidence to charge me, especially when I handed them copies of the recordings. Showing I made every effort to have her seen. I informed others to start recording their calls with him and his office. Within 7 months there was enough evidence against the office to have them shut down pending investigation by the state vet licensing board. The investigation was never completed as he "decided to retire, and sell his practice." Suddenly that was fine with the state board, except others came out of the woodwork reporting similar situations. "My cat was never a priority, I always had to wait 72-96 hours for a cat appointment but if my dog ate something she shouldn't have I could get seen within an hour, and it was the same doctor for both animals." The state ended up pulling licenses for several vet techs because they went along with his hatred of cats - which came out later when he was sued civilly for damages to one family's entire cat population - 10 cats over several years, all died while patients of his, and the family had the $ and the connections to sue. He had the damnable luck to die of old age before he got served with what was due to him, and his estate settled out of court for a healthy payout...which indicated just how wrong the family knew the guy was.
The area now has a MUCH better set of vets and several other practices have opened and from my friends' experiences things are VASTLY improved over a decade ago. As for the vet here, I cannot say enough awesome things about them, the fact I may not have a petco or petsmart nearby but the less than 2.5 mile round trip from the house to the vet and back...more than makes up for it. But despite the fact that Darla was a pain in the ass, and my vet for her was a royal douchecanoe I learned what NOT to tolerate in a vet, and what to like even more about the vet staff I have now and how much they're willing to let me learn.