I would switch her to a raw meaty diet. It's low in protein and high in water - great for dogs with kidney problems. Just because it's meat doesn't mean it's high in protein; meat is about 70% water.
There are several people I know that feed raw to dogs with kidney problems and chronic infections, and it seems to control and/or solve the problem. You can find them by joining the Raw Feeding (RF) Facebook group and doing a search. I hope that helps! Good luck