The 'My Boy Lollipop' hitmaker suffered a stroke, according to her friend and manager, Chris Blackwell, who also co-produced the 1964 hit, which became one of the top-selling ska songs of all time.
Chris paid a touching tribute to Millie, who he described as "a really sweet person", "very funny" and "really special".
He told the Jamaica Observer: "I would say she's the person who took ska international because it was her first hit record.
"It became a hit pretty much everywhere in the world.
"I went with her around the world because each of the territories wanted her to turn up and do TV shows and such, and it was just incredible how she handled it.
"She was such a sweet person, really a sweet person. Very funny, great sense of humour. She was really special."
The Island Records founder - who was speaking from New York - told the publication he hadn't seen Millie, who died in England, in over a decade.
Chris discovered Millie's music early on and persuaded her father, an overseer on a sugar plantation in Jamaica, to allow him to become her manager and take her to England in late 1963 when she was old enough to travel by herself.
Millie had said: “I hadn't planned on being a star, but I always wanted to be a singer, and I felt like it was my destiny to go to England.”
Chris was the one who suggested a cover of the R&B song 'My Boy Lollipop', which was originally recorded by Barbie Gaye in 1957.
And the song continues to be adored to this day and is still played on radio stations across the globe.
The ska hit was held off the number one spot on the Billboard Hot 100 in the US in 1964 by The Beatles and The Rolling Stones and it made it to number two in the UK.
The arrangement is credited to Ernest Ranglin, who plays the guitar, and the saxophone solo was replaced by the harmonica.
Millie had insisted that Rod Stewart played the mouth organ, but he denied this.
Millie's later releases, 'Sweet William' and 'Bloodshot Eyes' charted in the UK at number 30 and 48.
In 2012, Millie said she was planning to record new music and play in Jamaica for the first time in 40 years.
The singer/songwriter released three albums during her career, the LP 'My Boy Lollipop', 1965's 'Sings Fats Domino and 1970's 'Time Will Tell'.