Debra Tate and Anthony DiMaria, a nephew of hairstylist Jay Sebring, were among those who testified at the hearing at the Central California Women's Facility, according to Sandi Gibbons of the Los Angeles County District Attorney's Office.
Manson is next up for parole in May 2012. Watson is up in November 2011.
Atkins hardly looks the part of the cold-blooded murderer, but she has been described as one of the more vicious of the "Manson women."
If parole had been granted, it would have been an act of mercy that she so notoriously denied her most famous victim – an 8-months pregnant actress Sharon Tate, who was murdered in her Los Angeles home on Aug. 9, 1969 alongside Jay Sebring, Abigail Folger and Wojciech Frykowski. Teenager Steven Parent was also murdered that night in Tate's driveway for simply being in the wrong place at the wrong time.
In one of the most chilling moments of the Manson Family's crime spree was Atkins' account of how the actress pleaded for mercy for her unborn child.
"She asked me to let her baby live," Atkins said at a parole hearing 16 years ago. "I told her I didn't have mercy for her."
Cult-leader Manson, buddy Charles "Tex" Watson and two of his infamous "Manson women" -- Patricia Krenwinkel and Atkins -- were sentenced to death for the Tate murders and the slaying of grocery store executive Leno LaBianca and his wife Rosemary on Aug. 10, 1969. A third woman, Leslie van Houten, was convicted along with the others and sentenced to death on two counts of murder for her role in the LaBianca murders.
Anthony DiMaria, nephew of Jay Sebring, a hairstylist to the stars who died as he tried to protect Tate and her unborn child, said he will once again make the trek from Las Vegas to California in hopes of keeping his uncle's murderers out of society.
"She's more than a Manson follower," he said of Atkins. "She's a mass murderer."
Paroling Atkins because she was dying of cancer -- a disease he called "fate" -- would send the wrong message, especially given Manson's dark following as some kind of anti-hero, DiMaria told ABCNews.com.
"Like it or not she and these crimes have had a huge impact, obviously on our family but also culturally," he said.
Atkins had spent most of the last 38 years at the California Institution for Women in Corona, Calif., the same facility that houses Krenwinkel and van Houten. She was moved to Chowchilla last year after being hospitalized.
Thornton said Atkins has been an active inmate with a "well-documented record" of volunteerism and participation in events and groups dealing with personal growth, religion, substance abuse, self-help and fundraising.
She's also earned over the years "above average to excellent work performance ratings," Thornton said, and has held a variety of jobs working in laundry, maintenance and the yard crew as well as positions as a teacher's aide, a clerk and a porter.
Thornton said Atkins also logged five rules violations in her 38 years in prison, the most recent in March of 1993. She did not have specifics about the violations.
She's also been married twice while behind bars. Her second husband, James Whitehouse, has become her most vocal supporter.