Dee died Sunday morning at the Los Robles Hospital & Medical Center in Thousand Oaks, said Cynthia Mead, nursing supervisor.
She died of complications from kidney disease after nearly two weeks in the hospital, said Steve Blauner, a longtime family friend who represents Darin's estate. Blauner said Dee had been on dialysis for about four years.
"She didn't have a bad bone in her body," he told The Associated Press in a phone interview. "When she was a big star in the pictures and a top five at the box office, she treated the grip the exact same way she treated the head of the studio. She meant it. She wasn't phony."
At Universal Studios, Dee was cast mostly in teen movies such as "The Reluctant Debutante,""The Restless Years,""Tammy Tell Me True" and "Take Her She's Mine."
Occasionally, she was able to do secondary roles in other films, such as "Imitation of Life,""A Portrait In Black" and "Romanoff and Juliet."
At the height of her fame, Dee was arguably the biggest female teen idol of her time. "She was Gidget, and she was Tammy, and for a time she was young America's ideal," film critic Leonard Maltin once said of her.
After a one-month courtship, Dee married Darin in Elizabeth, N.J., in 1960. A son, Dodd Mitchell, was born to the couple the following year.
In 1965, with her divorce from Darin dampening her teen appeal, Dee was dropped by Universal.
"I thought they were my friends," she said in an interview that year with The Associated Press, referring to her former bosses. "But I found out on the last picture ('A Man Could Get Killed') that I was simply a piece of property to them. I begged them not to make me do the picture, but they insisted."
Born Alexandra Zuck on April 23, 1942, in Bayonne, N.J., Dee became a model while in grade school.
In a mid-career interview with The Associated Press, she explained her name change: "I used to sign vouchers and sign-out sheets with 'Alexandra Dee.' Somehow it stuck." When she was signed to her first film, she said, "'Sandra Dee' was the name they gave me."
Dee made an independent film "Rosie!" (1968), starring with Rosalind Russell, but her movie career dwindled after that.
Her name was resuscitated in 1978 with the film "Grease," which featured the song "Look At Me, I'm Sandra Dee" mocking her squeaky-clean image. But Dee didn't mind, Blauner said.
"She always had a big laugh about it. She had a great sense of humor," he said.
Blauner said her favorite films were the ones she made with Darin. Despite their divorce, he remained the love of her life, Blauner said.
In a March 1991 interview with People magazine, Dee said she was sexually abused as a child by her stepfather and pushed into stardom by her mother. Dee, who turned to pills and alcohol, said she hit bottom after her mother died in 1988.
"I couldn't function," she told People, adding that she began drinking more than a quart of scotch a day as her weight fell to 80 pounds. She said she stayed home almost constantly for three years. Her last film credit was for the 1983 movie "Lost."
Dee credited her son with helping her turn her life around. She began seeing a therapist regularly and hoped to land a job on a TV series.
Kate Bosworth portrayed Dee in last year's movie Beyond the Sea, a biography of Darin.
Actor Kevin Spacey, who directed and co-wrote the film and played Darin, has said Dee approved of the movie. "She called me...and said she loved it," he said last year.