Updated

The lawyer for a woman who allegedly lied to police about the disappearance of University of New Hampshire sophomore Elizabeth "Lizzi" Marriott last fall said she will plead guilty to all charges against her Thursday.

Kathryn McDonough of Portsmouth is charged with hindering prosecution, conspiracy and tampering with a witness in the death of 19-year-old Marriott, whom McDonough had befriended shortly around her disappearance.

Defense attorney Andrew Cotrupi would not comment Wednesday on what sentence McDonough would receive, but told The Associated Press he expects his client to be taken into custody after the hearing in Rockingham Superior Court.

Members of Marriott's family are expected to attend the change-of-plea hearing and to address the court. Robert Marriott, Lizzi's father, did not return a call seeking comment.

McDonough's ex-boyfriend, 30-year-old Seth Mazzaglia, is charged with first-degree murder for allegedly strangling Marriott during an attempted sexual assault Oct. 9 in the Dover apartment he shared with McDonough. Police say the couple told investigators they dumped her body into the waters off Peirce Island. It has never been recovered.

Prosecutors say Mazzaglia and McDonough plotted to tell investigators Marriott died during a consensual sex act. Senior Assistant Attorney General Jeffery Strelzin has stated adamantly there was nothing consensual about the circumstances surrounding Marriott's death, but has not revealed what evidence the state has to prove it.

Marriott's home was in Westborough, Mass. She had transferred to UNH last fall to major in marine biology. She commuted to campus from Chester, N.H., where she was living with relatives, and attended an evening class at UNH.

On the day she disappeared, she left a note for her aunt and uncle saying she was going to visit a friend after her night class and would be home by midnight. She also texted a friend that night that she planned to visit McDonough to watch a movie. Marriott and McDonough had met recently at a Greenland department store where they both worked.

McDonough initially told police Marriott never showed up that night.

Marriott's disappearance led to a massive search, and her family and friends distributed leaflets throughout the seacoast region seeking clues to her whereabouts. Mazzaglia was arrested and charged with her death four days after Marriott was last seen.

McDonough was arrested Christmas Eve and remained in custody until Jan. 2, when she was released on $35,000 bond on the condition she live with her parents in Portsmouth.

Her willingness to testify against Mazzaglia is expected to be a condition of her plea agreement. Mazzaglia returns to court July 31. He is being held without bond.