Personally, i would wait it out until she shows signs that she’s in pain. if she’s preforming almost perfectly fine, i don’t think there’s anything to worry. of course it’s a big decision as you’ve had her for so long, however it isn’t fair to her if you put her down and she isn’t in too much pain.
we have had my cats for 14 years, and have always been told they are half rag dolls since we adopted them
however i do not think they look half rag doll, but they sure act like it