It depends how highly elevated these are, and whether medications will affect those levels.
And also how much
kidney function she still has remaining. If there is anything to work from, your vet should be trying. Only as a last resort, and in the final stages, when EVERYTHING POSSIBLE has been tried, and does not work any more, should you consider having her put to sleep
This is a very helpful website if you need to read about Kidney Failure in dogs:
http://www.vetinfo.com/dkidney.