The Canadian star died at her home in Beverly Hills, California, last night (11.06.12) aged 94.
Ann's close friend and fellow actress, Anne Jeffreys, said she had been in declining health with heart problems.
Ann was best known for playing Scarlett's younger sister, Carreen, in 1939 film 'Gone With the Wind', and was one of its last surviving cast members.
Ann was initially refused the chance to be in 'Gone With the Wind' by MGM boss Louis B Mayer, who called her role a ''nothing part,'' but after she burst into tears and told him what a huge fan of the novel she was, he reconsidered.
In 2010 she told the Los Angeles Times newspaper: ''I just wanted to watch the book come to life.''
Speaking at the 70th anniversary of the film in 2009, she said: ''That 'nothing part' turned my golden years into platinum.''
Ann had come to prominence in the 30s playing Polly Benedict, girlfriend to Mickey Rooney's character in the Andy Hardy series of films, which continued into the 40s. She also appeared alongside singing cowboy hero Gene Autry and John Wayne in her film career.
Ann gave up films in the early 1950s but had a number of TV roles, including a recurring part in 'Perry Mason' before her retirement in 1976. She also has two stars on the Hollywood Walk Of Fame, one for TV and one for film.
Ann was married twice, to David May in 1942 - with whom she had daughter Gloria May - and to William Dozier, who she married after divorcing in 1953. They were together until his death in 1991.
Talking about her most iconic role in 1989, Ann said:''Our obituary will say we were in 'Gone With the Wind' and we'll be proud of it.''