I would avoid Clavamox in any cat who already has issues with eating since (as you know, it causes GI upset). If she has a suspected UTI, you're better off going with a Convenia injection or course of Zeniquin, depending on the type of bacteria she has.
How high are her renal values? (BUN, creatinine, phosphorus) And what is her potassium? If her phosphorus is >5.0, we recommend putting them on a phosphorus binder (aluminum hydroxide), because a high phosphorus level caused by renal disease makes cats nauseous and less likely to eat well.
Also, all renal cats should be on famotidine (Pepcid) to help with the acid in the stomach caused by increased renal values. Controlling an acidic stomach helps them feel less nauseous and eat better.
Since pilling is a problem for most people, we have medications compounded into a transdermal cream form that you rub a small amount onto the hairless aspect of the ear flap to absorb through the skin. We often have 3 or 4 medications compounded into the same cream so you don't have to give multiple different medications at once orally. For renal kitties, we mostly use famotidine (Pepcid) as an antacid, ondansetron (Zofran) for nausea/vomiting, buprenorphine for pain (especially for older kitties who have arthritis), and cyproheptadine for appetite stimulant. We also use mirtazapine in cats as an appetite stimulant since it doesn't have to be given as often as cyproheptadine and also has anti-nausea properties.
The transdermal cream and aluminum hydroxide can be made at any compounding pharmacy. There are several in our immediate area that makes it, and its a god send for most of our clients. You should really look into it if your girl is difficult to orally medicate.
Depending on what BUN and creatinine are, you may want to consider doing SQ fluids, even if its just a few times a week. Water she gains from food is literally a drop in the bucket compared to what her kidneys need to stay happy, especially if her values are high. It's good to mix extra water into food, use pet water fountains, etc, but its no substitute for SQ fluids.
Since my clinic is feline-only and renal disease is probably the most common disease we see in cats, we've become very adept at treating it and having clients successfully treat it for many years at home. If you have any questions, feel free to PM me