The cause of death has not yet been reported.
Nancy Barbato and Frank Sinatra were high school sweethearts. Frank who passed away on May 14, 1998, from all accounts, took care of Nancy after their divorce for the remainder of her life. "Godspeed, Momma. Thank you for everything", she wrote.More news: United Nations aid chief: 'clear evidence of humanitarian need' in N. Korea
Nancy Sinatra Sr. married Frank Sinatra Sr., then an aspiring lounge singer, in 1939.
After he became a pop-music sensation in the 1940s, the couple moved to Los Angeles, where the singer would also become a movie star, raconteur and notorious womaniser.
Nancy and Frank married in their teens and had three children together. It was there that Nancy (best known for her hit song, "These Boots Are Made For Walkin") and Frank Jr. were born.More news: Congress to Trump: Cancel Putin summit after new Mueller indictments
Sadly, the marriage eventually crumbled as Nancy filed for a legal separation on the grounds of his mental cruelty amid reports that he embarked on another affair, this time with Hollywood icon, Ava Gardner, and they were divorced by 1951.
In this October 23, 1946 file photo, singer Frank Sinatra and his wife Nancy smile broadly as they leave a Hollywood night club.
She is thought to have remained friends with her ex-husband up until his death and he would reportedly put in requests for various Italian dishes she was a expert in over the years.More news: 'Unprecedented Level of Animus!' Strzok Gets His Smackdown for Anti-Trump Bias