CONCORD, N.H. — A New Hampshire woman is free after serving a three-year prison sentence for luring a co-worker to her apartment in 2012 as a sex offering to her domineering boyfriend, then helping him dispose of the co-worker’s body after authorities say he strangled and raped the woman.

Kathryn “Kat” McDonough was released from the women’s prison in Goffstown at 12:05 a.m. Saturday, said corrections spokesman Jeff Lyons.

The 22-year-old pleaded guilty in 2013 to lying about the disappearance and death of 19-year-old Elizabeth “Lizzi” Marriott, of Westborough, Massachusetts. She testified against Seth Mazzaglia, describing their sexual relationship marked by bondage and sadomasochism. He was convicted of murder, and is serving a sentence of life without parole.

Marriott was killed only weeks after beginning her sophomore year as a marine biology major at the University of New Hampshire in Durham. She had worked with McDonough at a department store. Her body has not been recovered.

McDonough first told investigators that Marriott died during rough sex between them using restraints. After getting immunity from prosecution, she changed her story, saying Mazzaglia killed Marriott after she rejected him.

As her release from prison neared, she planned to live with her father on the seacoast. The parole board was concerned that she not live so close to the scene of the crimes. Because of her notoriety, board members said, McDonough would have difficulty finding a job or even being in public near where the crime occurred. But with the sentence served, she is under no obligation to follow the board’s guidelines, and the board can’t impose any conditions on her. She doesn’t have to tell authorities where she will live.