During the worst of her disease, she once said, she ate only two small squares of chocolate and four to five cornflakes per day.
Caro died Nov. 17 after returning to Paris from a business trip to Tokyo, but her death was not made public until Wednesday because her father wanted it kept quiet, her friend and colleague Kim Warani told AOL News.
Warani, 26, who directed Caro in a number of small Paris-area plays over the past four years, said she fell into a coma several days after coming home from Japan. Her father took her to a hospital, where her condition rapidly worsened.
"She died from the effects of being so weakened by anorexia," said Warani, adding that Caro had been hospitalized for pneumonia this summer. "She lost a lot of weight again in recent months."
"My mother's big phobia was that I would grow," she said in an interview with CBS News last year to promote her 2008 memoir, "The Little Girl Who Didn't Want to Get Fat."
"She spent her time measuring my height. She wouldn't let me go outside because she'd heard that fresh air makes children grow, and that's why I was kept at home. It was completely traumatic. She wanted me to be her little girl forever."
Caro became famous overnight when she posed nude for a shocking Italian ad campaign for the Nolita clothing line in 2007. The unforgettable images showed Caro's skeletal and emaciated frame, complete with bones sticking out from sagging skin.
The photographs were shown in newspapers and billboards all over Europe and in some parts of the U.S. and titled "No Anorexia." The hope was that Caro's alarming condition would help other anorexics and discourage the use of super-skinny fashion models.
Caro, who stood 5 feet 6 inches tall, said she weighed about 59 pounds at the time. In recent years she reportedly had gained some weight, vacillating between 66 and 93 pounds, according to an online resume for her work as an actress.
"It's real suffering and it goes deep," Caro told CBS News. "I've suffered enormously from seeing how people look at me and judge me."
Warani said Caro was under the care of doctors for years and in and out of hospitals. She had been in a coma once before.
"She fell down a lot because she was so weak," Warani said. "She was always covered with cuts and bruises that took a long time to heal because of her sickness."
But as fragile and ill as she looked, Caro always had a strong will, said her friend, the Swiss singer Vincent Bigler.
"She was very strong-minded," said Bigler, who wrote a song inspired by seeing a program about Caro on European TV. The song was called "J'ai Fin," which is a play on words. The expression means "I am finished" in French, but the words sound like "J'ai faim," which means "I'm hungry."
Caro later contacted him and suggested they collaborate on a video of the song. Bigler said they could never reach an agreement on how much he would pay her to travel to Switzerland and work with him.
"She knew exactly what she wanted," Bigler said. "I hoped someday we'd reach a compromise. But she doesn't give up easily."
Bigler said Caro represented bravery to him.
"She didn't worry about what people thought about how she looked in the pictures," he said. "She was so sick, very weak, losing her teeth and hair. She wanted to send a strong message out about anorexia."
Caro's friends said today that she conducted herself as if she wasn't sick, even though she acknowledged her anorexia and hoped to overcome it some day.
She pursued her career with great confidence, said Sylvie Fabregon, a Paris modeling agency booker. Fabregon said Caro came to see her in 2007 hoping to be taken on by the agency as a model. "I told her no, she looked too sick physically," she said. "She was not very happy to hear that."
But shortly after Fabregon met Caro, she got a call from Italian photographer Oliviero Toscani, who was seeking a very thin model for a campaign. Fabregon put him in touch with Caro and she was hired for the fashion campaign.
Fabregon said Caro never did other real modeling, though her resume lists work with other photographers.
Fabregon said the Italian ad campaign was designed to show the horrors of anorexia, but that it sometimes backfired. Pictures of Caro can often be found on the numerous so-called "pro-ana" sites on the Internet that encourage anorexia.
Warani said she believes that the ad campaign did not help Caro with her illness, either.
"I think she was trapped in a vicious cycle," said Warani. "Those pictures made her famous and the center of attention and in some ways that may have been hard to give up."
Caro achieved fame in the U.S. as well, especially after appearing with Jessica Simpson on her interview show, "The Price of Beauty."
Caro made many references to her troubled but "very close" relationship with her mother in her book and on her blog. She spoke of her mother's disapproval if she gained weight as a child.
"I wanted to have the body of a child forever, to make my mother happy," she once said.
Her parents are now divorced, said Warani. And while she confirmed that what Caro said about her mother was true, Warani said the family still cared about one another very much.
Her parents tried to help her as much as they could, she said.
Warani attended Caro's funeral in Paris with Caro's family and friends. "Her mother was sitting there, totally devastated," Warani said.