A 21-year-old woman formerly from the Twin Cities has admitted to slashing her aunt's neck in a Fond du Lac Indian reservation home west of Duluth and leaving her to bleed to death.

Lydia M. Barney, of Brookston, pleaded guilty Tuesday in St. Louis County District Court to the intentional second-degree murder of her aunt, Waubunoquay D. Randall, 31, at the victim's Stoney Brook Township home in October.

Barney, 21, admitted Tuesday in court that she used a kitchen knife to murder Randall, saying, "I knew I was killing her, I didn't want her to suffer, I killed her, yes."

Randall's body was found Oct. 19, a day after she was last seen with Barney in the victim's home. An autopsy determined that Randall died from cuts to her carotid artery and jugular vein in her neck "causing a fatal loss of blood," according to the criminal complaint.

Barney's sentencing is scheduled for July 16. Her criminal history in Minnesota includes five convictions on various theft counts in the past three years, with four of those offenses occurring in the Twin Cities. As recently as 2012 she was living in Richfield.

Randall's husband, who lives in nearby Cloquet, had been jailed in the killing early on but was released and cleared of any role in the crime.

About the time investigators were in Randall's house immediately after the killing, a suspicious fire was burning in a home down the street. Barney admitted breaking into the home. Women's clothes were found on fire in an oven, and that incident may have been related to Randall's death, according to investigators.

Investigators said Barney never offered a coherent explanation for killing her aunt. Barney was high on an addictive anti-seizure medication at the time and became afraid of Randall at some point, investigators added.

In one hearing, Barney's attorney argued without success that the defendant was mentally incompetent to stand trial because of attention deficit hyperactivity disorder, making her incapable to assist in her own defense.