I am sorry to hear you are worried about Coco. My name is Rebecca. I am a veterinarian and will do my best to help.
That is a high BUN and phosphorus. Do you know her creatinine which is the most important kidney number on blood tests?
Has a urinalysis been done? There are things we can learn from the urine about the kidneys that blood tests don't tell us.
There are two forms of kidney failure: chronic, and acute. With acute kidney failure, if you treat aggressively with fluid therapy sometimes you can turn things around. If there is protein in the urine, a drug called an ACE inhibitor may help.
If this is chronic kidney disease, then aggressive fluid therapy might make her feel better for awhile, but the damage may be irreversible. If you want to do all you can, you could take her to a vet clinic that is open 24/7 and start IV fluids for at least 2 days. After that, I would recheck the blood test results to see if the BUN and creatinine and phosphorus are improving and continue fluids if they are.
Has she possibly eaten any grapes or raisins recently? They can cause acute kidney failure sometimes.
I am so sorry to hear about this. You are right to be worried. Please let me know if I can answer any more of your questions, and if this is helpful.