How old is your dog?
How long has she been ill?
When did you start the new diet?
What other treatments are you using for her condition?
Lets start with the basics first:
The kidneys principally act to remove toxins from the blood stream through the urine. The kidneys have to be nearly 70% damaged to show elevations of enzymes in the blood. Damage could be occurring several months to several years before kidney failure is evident. Unless it is the result of a toxic ingestion like antifreeze. In the beginning the kidneys cope with failure by excreting waste at a lower concentration in a larger volume. This can be checked through the specific gravity in a urinalysis.
There are several diseases that can lead to renal failure: Bacterial kidney infections, damage to the filtering mechanism, tumors, aging. The signs of kidney failure can vary but include, vomiting, nausea, decreased appetite, weight loss, increased thirst, increased urination, poor coat, lethargy, diarrhea, and mouth ulcers.
Most dogs in renal failure have both the BUN and CREA significantly elevated. Treatment with intravenous fluid or subcutaneous fluids depending on severity should be initiated. You can do the fluids under the skin at home with a short lesson from the veterinarian. Also, a trial of antibiotics I would recommend in case there is possibility of kidney infection. A dog with suspected renal failure needs to be put on a low protein diet. A lower protein diet will decrease the amount of waste products in the bloodstream. There are prescription diets that make this easier. I have seen more dogs take to the K/D diet over all the other ones, but it is a preferential of taste amongst dogs. I would recommend you stick with a canned diet as these provide more moisture than the standard dry foods. Also, discuss with your veterinarian about adding vitamin supplements like vitamin B and C. Dogs in renal failure lose these vitamins and need supplementation. The hardest part is getting a sick dog to eat. The food just doesn't taste good to them and at times it might even be recommended to give the pet anything just so that they will eat.
After saying all of this I really think your girl should have her blood work reevaluated. If her numbers are significantly higher she would likely benefit from being placed on IV fluids for a few days to flush the toxins from her bloodstream and then reevaluate her progress at the end of these four days. If her numbers had a 50% or more drop then I would continue to pursue treatment with her but giving her fluids under the skin at home. I really urge you to take her into a vet or an emergency center first thing tomorrow if it is not feasible tonight. Start giving her pepcid daily to help with the acids on her stomach and try feeding her boiled chicken and rice. Right now the food tastes like metal so it will be difficult to get her to eat but you can get a syringe and baby food and start force feeding her after the pepcid has been in for 30minutes. Dogs who are in renal failure are also usually very anemic this would increase her lethargy so food right now if very important. At this point I don't care what you get her to eat just that she is eating something. Once the toxins are flushed her appetite should return. If not there may be something else occurring. Also, try adding chicken broth to her water to tempt her to drink more. Make sure she is also able to urinate. If you aren't seeing any urine from her then her kidneys have completely shut down and the situation is not good.
Please let me know if further assistance is needed.