Van Houten spent the last 44 years in custody after her conviction at the age of 19 with Manson and two other women in the infamous Tate-LaBianca murders. She was most recently denied parole in 2010.
Van Houten, 63, told a California parole board in unprecedented detail Wednesday how committed she was to the murders Manson ordered and acknowledged that Manson "could never have done what he did without people like me," but asserted she has changed and is trying to live a life of healing.
"I know I did something that is unforgiveable, but I can create a world where I make amends," Van Houten said. "I'm trying to be someone who lives a life for healing rather than destruction."
But Board of Parole Hearings Commissioner Jeffrey Ferguson told Van Houten she had failed to explain how someone as intelligent and well-bred as she was could have committed the "cruel and atrocious" murders of Leno and Rosemary LaBianca, and the panel rejected her bid.
Van Houten will be eligible for another parole hearing in five years.
Van Houten's lawyer, Michael Satris, argued his client has totally reformed herself, saying Van Houten's value system is the complete opposite of 1969 when "she was following the teachings of a false prophet."
"She is living a life of amends for her crime on a daily basis," he said. "Everything she does now is to be of service and benefit to the world."
Van Houten has been commended before for her work helping elderly women inmates at the California Institution for Women. She earned two college degrees while in custody.
Other members of Manson's murderous "family" have lost bids for parole. One former Manson follower, Bruce Davis, actually was approved for parole last year only to have Gov. Jerry Brown veto the plan in March.
Van Houten was convicted of murder and conspiracy for her role in the slayings of wealthy grocers Leno and Rosemary La Bianca, who were stabbed to death in August 1969, one night after Manson's followers killed actress Sharon Tate and four others including celebrity hairdresser Jay Sebring, coffee heiress Abigail Folger, filmmaker Voityck Frykowksi and Steven Parent, a friend of the Tate estate's caretaker.
While she did not participate in the Tate killings, Van Houten went along the next night when the LaBiancas were slain in their home. During the penalty phase of her trial she confessed to joining in stabbing Mrs. LaBianca after she was dead.
The Associated Press contributed to this report.