Stone said the arrival of her daughter has significantly improved Harmon's mood, adding that her mother instantly falls in love with Sadie everytime she "meets" her.
"My mom loves her," Stone told TODAY. "She was here for Thanksgiving and she said, 'Why can't I take the baby? I want to take her home?' It's put some pep in her step."
"But her short term memory is gone. Every time I say, 'Meet your granddaughter, Sadie,' she'll forget whose baby it is again five minutes later. She gets so excited all over again," Stone added.
Harmon was born in Japan, but moved to the U.S. after marrying her husband, Bob Harmon more than 46 years ago. Despite her illness, she still recalls some aspects of her Japanese culture.
"She remembers the words to an old Japanese lullaby song called 'Donguri Korokoro' about an acorn and an eel, and sings it to Sadie," Stone said. "I only video the good moments, I don’t video the bad moments - and there are plenty of bad moments."