My Precious Mitou

I'm hoping for some cyber support to help me get through what are probably the last days of my precious tiny almost 20 year old (on July 16) Siamese, Mitou. Her kidneys are failing we know because of a blood test but until she stopped eating last Sunday (except if I hand feed her a little turkey) she seemed to be feeling ok. She's constipated, is losing weight, her back legs are wobbly and she sometimes loses her balance but I don't know if she's in pain. I don't know if it is easier for her to let nature take it's course or to take her to the vet. I have a call in to the vet and am waiting to hear back. We've had 17 wonderful very loving years together and I want to do the right thing. Please help me with some insights. Thank you. Judy