Midge Turk Richardson, a former nun and parochial school principal in Los Angeles who cast off her habit for the world of New York publishing, where she reigned for nearly two decades as editor of Seventeen magazine, has died. She was 82.

Richardson, who was found in her New York City home Dec. 17, appeared to have died in her sleep from natural causes, according to her stepson, Kevin Richardson.

A Los Angeles native, Richardson spent 18 years as a nun in the order of the Sisters of the Immaculate Heart of Mary, including seven years as superintendent of Our Lady Queen of Angels High School.

She left the order in 1966, a few years before it disbanded in a dispute with Cardinal James Francis McIntyre of the Los Angeles Archdiocese over reforms addressed by the Second Vatican Council.

Richardson described the personal upheaval of those years in a 1971 memoir, "The Buried Life," which one reviewer praised as "more than the usual litany of disenchantment with religious life."

In her new life, she joined the New York social swirl and married Hamilton Richardson, a former Davis Cup tennis star who had gone into the oil and gas business.

In 1975, she became editor of Seventeen, the iconic magazine for teenage girls, founded in 1944. As the publication's longest-serving editor, Richardson played a central role in expanding its coverage beyond beauty and fashion to college, careers and issues such as feminism and human rights.

She also featured frank discussions of such topics as sex, abortion, gynecological health, eating disorders and depression. She wrote a regular column called "Sex and Your Body."

"She was such a legend," said Ann Shoket, the magazine's current editor. "The magazine's role under Midge was to explain the world to young women, help them see beyond what was happening in their lives."

Richardson often said she saw her work with the magazine as a natural extension of her previous role as an educator.

"Life is moving so much faster for this generation," she told the Chicago Tribune in 1989. "They're talking about jobs and college when they're 15.... They are making a lot of very serious choices about sex at a very early age. We have to educate them much sooner to deal with this."