"She was a blessing and the light of my life", she wrote.
They were divorced in 1951, just weeks before he married Ava.
She outlived her husband, who died in 1998.
Her daughter, Nancy Sinatra Jr, tweeted that her mother died on Friday and a posting on her webpage said she died at 6:02pm, but didn't indicate where.
MRS Sinatra was a handsome and classy woman, who whenever you would read about her in articles or in forums on Facebook, was highly respected.
Nancy Sinatra left Frank after his affair with actress Ava Gardner became public knowledge.
Nancy and Frank Sinatra began dating as teenagers before marrying at a church in Jersey City, New Jersey, on February 4, 1939, reports the Associated Press. "Godspeed, Momma. Thank you for everything", Nancy wrote.
While Frank tried to get his career started in the music industry, Nancy worked as a secretary.
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They Wednesday in 1939 at the Our Lady of the Sorrows church in Jersey, then moved into a modest NY apartment while Nancy worked as a secretary.
When Sinatra eventually became a huge success at the beginning of the 1940's, they went on to move to Los Angeles, where he became a movie star and a famous ladies' man.
Nancy Sinatra never remarried, but there was little enmity between she and her former husband.
After he divorced Gardner, Sinatra went on to marry Mia Farrow and then Barbara Marx.
As Nancy Barbato, she made two TV and film appearances, one in her daughter Nancy's 1975 concert film, Nancy and Lee in Las Vegas, and in 1974 on her friend Dinah Shore's talk show.
The two had three children together, Nancy, Frank Sinatra Jr. and Tina Sinatra.
Sinatra's hit song, "She's Funny That Way", plays in the background.