I am sorry about your girl's diagnosis.
It seems of course, sadly, that there is no cure for kidney failure, but only management and palliative treatments for symptoms as and when they arise.
Has her blood Phosphorus level been checked? It's the high blood Phosphorus which can be responsible for nausea and loss of appetite. It is possible sometimes for symptoms to be relieved by the use of the appropriate "Phosphorus-binder".
Sometimes just plain calcium carbonate can help with that. It can be obtained from plain unflavoured Tums tablets, or from powdered eggshell added to food in an amount suitable for a dog's weight.
But it's wise to check with the vet, because sometimes other Phosphorus-binders are used.
Sometimes, if the Phosphorus levels are lowered, the appetite can come back a bit, and the nausea lessened.
My own dog developed mild kidney failure in 2011. She was asymptomatic except for peeing and drinking more, and happy at the time. You'd never guess she had kidney issues.
She did, however, take to the Royal Canin renal diet, both dry and canned, and I did some home cooking for her too.
The vet prescribed an ACE inhibitor.
In a few weeks and over the next few months her creatinine and BUN came right down. So it seemed a combination of diet alteration and ACE inhibitor helped her.
Sadly though, she passed away from hemangiosarcoma the following June.
I have heard that green tripe is well-tolerated by dogs with renal failure. I think it stinks a bit while cooking though!
Vegetables, pasta, boiled potatoes, rice etc are all okay and can be added to the food. Not much protein, but will provide energy.
My dog was allowed some boiled chicken breast, white fish, and cooked egg too. BUT she had very early-stage kiney failure which was different to what is happening with your dog.
Bless her, and I hope you can find some management which will give her more time, and help her symptoms.