I just got a cat from a family member that could not longer take care of.............?

Yes that is old for a cat but I know of a cat that lived to 25 years old. First of all, I want to say that it is very humane of you to have taken the cat in the first place. Most people would want a kitten. I think that as long as you have taken her to the vet and the vet said that she was healthy for her age then just continue to care for her. I'm sure that when you show her affection she gets very pionate about it since she didn't get affection at her other home. If she gets sick in any way that can't be easily treated then I would put her down rather than spend alot of money and put her through surgery or whatever. I have one suggestion that you may already be doing. A cat that old needs to be put on good cat food for older cats. I suggest w/d or Iams. You can get it at most pet stores or vet clinics. It is a little expensive but may help her live a little longer. Good Luck with Gramma Kitty!