Condolences to you and your family, Marc. I lost my Mother in 2011 at age 77. She fell and broke her hip a few years earlier, and just never fully recovered from that. The downhill slide was fast. When I visited her the day before she died, she didn't even know who I was. She, too, had been suffering from various medical maladies. It seems sad to say that it was a relief to see her go, but the end of suffering is always a good thing.
My Wife just lost her maternal Grandmother last March at age 95. Her eyesight was almost completely gone, and her hearing wasn't much better. She had no short-term memory at all anymore, and was starting to repeat herself a lot. She had a stroke one morning, refused to eat, and died about two weeks later.
99 is a very long and full life. Think of the incredible changes she must have experienced over the course of a century ...
What a magnificent journey.