My Lady is a rescue (adopted at age 4.5). She had seizures three days after I adopted her and was officially diagnosed with epilepsy a month later. A year and a half later, she was diagnosed with diabetes. Over the next couple of years she was diagnosed with crippling arthritis, allergies, thyroid disease, and a heart murmur. She almost died twice when she was eight. No one, especially my vets, expected her to make ten years old.
She will be 16 this year.
Her vision isn't that great. She was never the sharpest tool in the shed so her more frequent "senior moments" aren't that noticeable. I am like her full time nurse with insulin injections and all her meds.
I learned many years ago to stop worrying about when I was going to lose her and just enjoy each and every day I have with her. I hope you can do that with your Lucy.