Marie was found dead at her Pasadena home Sunday, Pasadena Police Lt. Diego Torres said. Police and paramedics were called to her home about 3 p.m. after her daughter found her unconscious, Torres said.
Reviewing her performance in 1981 at the Long Beach Arena, Dennis Hunt wrote in The Times: "A tiny young woman with a powerful voice, Marie is a terrific singer and, quite frankly, better than nearly all her black competitors."
Born Mary Christine Brockert on March 5, 1956, in Santa Monica, Marie was raised in a predominantly black area of Venice and began singing professionally at age 8. Soon after graduating from Venice High School she signed with Motown Records, where she met funk music pioneer Rick James, who would become her mentor, musical collaborator and lover, a relationship she described as "fiery."
He produced her 1979 debut album, "Wild and Peaceful," which went gold and featured her first hit single, a duet with James called "I'm a Sucker for Your Love."
She recounted later that Motown founder Berry Gordy Jr., unsure how black audiences might react to her image, decided the album cover should feature a seascape with clouds rather than her photograph.
"He just wanted people to hear the music first, and then it wouldn't matter to people what color I was," she told the Boston Globe in 2004.
Many R&B enthusiasts who loved her strong, bluesy vocals didn't realize she was white until her photograph was featured on her second album, "Lady T" in 1980. By then she already had a large following in the black community.
In an effort to reach a broader pop audience, she signed on as the opening act on the Shaun Cassidy tour in 1979, which made for an unlikely match-up. Cassidy's fans were mostly young white girls.
"It was a rough situation for me given the way I sing and with my band being black," Marie told The Times in 1980. "Those young girls didn't know my music, and they couldn't really relate to me or the band."
Marie quarreled with Motown over royalties and fought to be released from her contract. The legal battle, which was settled in the early 1980s, resulted in the Brockert Initiative, named for her, which curbs a record company's power to keep musicians under contract while refusing to release their music.
"It wasn't something I set out to do," she told The Times in 2004. "I just wanted to get away from Motown and have a good life. But it helped a lot of people, like Luther Vandross and the Mary Jane Girls and a lot of different artists, to be able to get out of their contracts."
Marie, sometimes called the "Ivory Queen of Soul," went on to produce her own albums. She largely vanished from the public eye in the early 1990s after the birth of her daughter, Alia, saying she wanted to devote herself to motherhood. In 2004 she put out her first new album in a decade, "La Dona," featuring the track "Still in Love," which earned her a Grammy nomination.
That year, she was devastated by the death of James, with whom she had been touring, and stopped working for a time. She began touring again in recent years after battling a prescription-drug addiction.
A complete list of survivors was not available.