Ah, I forgot to mention; if you must have kitty off the bed, get either a heating pad and place a towel over it or get one of those plug in-self-warming kitty/doggie beds. At least then your cat will be toasty and warm as he sleeps.
Remember, old age hits us all; it's up to us to be considerate and kind to the frailties of those suffering from age related symptoms.
After all, we'll all get there eventually, so we should set the standard for how WE want to be treated when we do.
No leak diapers for incontinent pets. That will at least deal with the bed wetting issue. Use nature's miracle to clean up the mess, btw, to remove the smell entirely.
Otherwise, be sure your cat has access to soft foods that are easy to eat, just in case the lack of appetite is due to an inability to chew.
The above advice by ZQ is right on the money. Look into those tests, most of the above mentioned illnesses are very treatable with medication and/or proper nutrition.
I hope that the vet checked her for kidney disease. That's a blood test that checks the BUN levels and was her urine tested for excess protein in it? Kidney problems will first show up in their urine, and when it starts getting worse-it shows up in the blood. Kidney problems causes excessive thirst and urination that is very diluted (not normal yellow, but clear). I'm talking A LOT of urinating, and with that much urination there could be leaks.
Diabetes and hyperthyroid in cats causes excessive urination, too that could result in leaks.
I wish I had some ideas that would help you out with kitty sleeping in your bed, but I really can't. Hopefully, if these tests haven't been done yet, then these suggestions could help you to find the exact cause and you'll be able to stop this problem completely. So, hopefully this will help you some.
Have you tried to google urine leakage in cats yet? That's what I would do, and you may find even more ideas than what I've listed here!