Wanda Barzee, 72, quietly left the state prison in the Salt Lake City suburb of Draper, avoiding a throng of reporters gathered outside.
Court documents say she will stay in unspecified emergency housing chosen by her probation officer until another home is approved.
Barzee's release followed a surprise announcement last week that Utah authorities had miscalculated her sentence and she would be freed earlier than expected.
Under the terms of her release, Barzee must undergo mental health treatment and not contact Smart and her family.
Smart, now 30, has said she was shocked and disappointed by the announcement.
Smart recalled some of the horrors she experienced as a 14-year-old when she was snatched from her Salt Lake City home in 2002 by Barzee's then-husband, street preacher Brian David Mitchell.
Smart said last week that Barzee saw her as a slave during the nine months she was held by the couple and encouraged Mitchell to rape her.
"So do I believe she's dangerous? Yes," Smart said.
MORE: Elizabeth Smart's message to siblings allegedly held captive: 'Life is not as dark'
An Instagram post early Wednesday, Smart urged her supporters to watch out for "anyone who would seek to hurt or take advantage."
Smart did not immediately speak out publicly after Barzee was released later in the day.
Barzee's attorney Scott Williams said there's no reliable evidence that his client remains a threat to anyone.
"It is unfair and counterproductive," Williams told reporters, adding that Barzee wants to be left alone and will comply with the conditions of her supervised release.
He said he's concerned about her safety but did not elaborate.
Ed Smart, the victim's father, said he's glad Barzee will be watched over closely by federal agents during her five years of supervised release, but he's concerned about reports that she still believes Mitchell's ideas.
Aiding Mitchell in following his so-called divine revelations prompted Barzee to help him kidnap Elizabeth Smart and even sit next to her as Mitchell raped her, Ed Smart said.
"My hope is that she won't be a problem," he said of Barzee. "I do know how she treated Elizabeth during that time, and I still feel like she's very capable of doing the same thing."
Smart, now a married mother and activist for victims' rights, wrote on Instagram over the weekend that she's taken precautions and won't let her life be disrupted by the release of Barzee.
"I lived in absolute fear and terror for nine months, no matter the outcome I will not do so again," Smart wrote.
Smart was found in captivity while walking with Barzee and Mitchell on a street in suburban Sandy by people who recognized the abductors from media reports. Mitchell is serving a life sentence after being convicted of kidnapping and rape.
As another condition of her release, Barzee was placed on the Utah sex offender registry, but her address was still listed online Wednesday as the Utah prison. Her mug shot on the registry shows her with a wide smile, blue eyes and chin-length gray hair.
She's also voluntarily agreed to stay away from places frequented by the Smart family, Williams said.
Barzee could be returned to prison if she violates the terms of her release.
Barzee's niece Tina Mace has said her aunt's testimony against Mitchell seemed like a turning point, but her mental state appears to have changed in prison. Mace said she's unaware of any family members who would give Barzee a place to live.
Barzee was treated at Utah State Hospital for about five years following her arrest. She testified in 2010 against Mitchell and was given a plea deal on state and federal charges. She was transferred to the Utah prison in 2016 after finishing a federal sentence in Texas.
The Utah Board of Pardons and Parole initially set a 2024 release date. Her attorney questioned whether the term included time Barzee had served in a federal prison. The board decided last week that she had served her sentence.