Barbara married Frank in 1976 and remained his wife for almost 22 years - the longest of his 4 marriages.
The Barbara Sinatra Children's Center director John Thoresen told Fox News Sinatra died of natural causes, and she was "comfortably surrounded by family and friends" at the time of her death.
Having a famous spouse wasn't unusual for her, as Barbara Sinatra's first marriage was to one of the Marx Brothers, Zeppo.
She had a successful modeling career after she graduated from the school.
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She Wednesday the singing legend back in 1976, following her split from American actor Zeppo Marx.
She remained active at the center until recently, pushing for creation of the video program just past year and making sure the children had anything they needed, Thoresen said.
Sinatra is survived by her son Oliver Marx and granddaughter Carina Blakeley Marx.
"I've tried to analyse it", she told The Desert Sun, of her attraction and subsequent romance with Sinatra. "You worry about new ones, '", Barbara previously said.
The family requests that memorial gifts be directed to the Barbara Sinatra Center for Abused Children, 39000 Bob Hope Drive, Rancho Mirage, CA, 92270.
In the years since, Thoresen said, more than 20,000 children have been treated at the center in the desert city of Rancho Mirage and hundreds of thousands more throughout the world through videos it provides.