An Idaho nurse has pleaded guilty to tampering with physical evidence in the murder investigation of missing Colorado mother Kelsey Berreth, and as part of her plea agreement, she’ll testify against Kelsey’s fiance, Patrick Frazee.

Krystal Jean Lee, 32, was in tears as she told a Teller County judge that she knew Frazee killed someone and that she helped dispose of the victim’s cellphone. She faces up to 18 months in prison for the felony charge and will be sentenced after Frazee’s trial.

“I learned that Patrick Frazee had committed a homicide,” Lee told the court, while reading from a statement. “I knew that law enforcement would be investigating that crime.” Lee, a divorced mother of two, said she “moved” Kelsey’s phone between Nov. 24 and 25 “to impair the phone’s availability” in what was then only a missing persons probe.

Friday’s hearing added more fuel to the mystery of what happened to Kelsey Berreth, a flight instructor who vanished on Thanksgiving Day and is presumed dead. Authorities have largely kept the particulars of the case—including a suspected motive, and the relationship between Frazee and Lee—under wraps.

Frazee was the last person to see Kelsey alive during a custody exchange of the couple’s daughter, Kaylee, on Thanksgiving. The cattle rancher, who lived with his mother on a Florissant property, reportedly met Kelsey online before she moved from Washington to Colorado in 2016 to be with him.

Woodland Park police arrested Frazee in December. Authorities believe Frazee may have enlisted help in killing Kelsey and charged him with two counts of first-degree murder and three counts of solicitation to commit first-degree murder. Frazee likely murdered Kelsey at her Woodland Park townhouse, investigators say.

On Friday, 4th Judicial District Attorney Dan May declined to comment on anything that wasn’t already in the court record, including whether Kelsey’s phone was located, or whether cops are any closer to recovering Kelsey’s body.

“When Kelsey was a missing person, we were all hoping this would end much more favorably than it has at this point,” May said. “It’s a horrible tragedy. Horrible tragedy for their family. Horrible tragedy for our community.”

Lee, who also goes by Krystal Kenney, is barred from speaking to the press as part of her plea deal. Two relatives previously told ABC News that Lee only helped Frazee, whom she reportedly met at a rodeo, because he threatened her life.

Last month, an Idaho couple came forward with allegations from one of their employees, who was close to Lee. Joe and Patty Rockstahl, who run a Twin Falls law firm, said that employee approached them in October and claimed a man named Patrick had asked Lee “to kill the mother of his child.”

The Rockstahls said they suggested Lee come in and talk with them, but that Lee never did. They didn’t have enough information to go to police, they said—until they saw Kelsey’s mother on national television, pleading for the public’s help.

“I think the mother that had the courage and go on TV when her daughter was missing, saying that someone knew where she was at,” Patty Rockstahl told KMVT. “At that point in my mind I thought that Patrick, and that was the only name I had heard him called, I didn’t know his last name, had done something to her daughter and he knew where she was at.”

In another KMVT interview last month, Patty Rockstahl reiterated suggestions that Lee was threatened by Frazee: “From what I can gather, I believe she really cared for Patrick but, I also think she was afraid.” The Rockstahls said Lee had been traveling to Colorado before Kelsey’s alleged slaying. “She had known him since she was 18 years old, right out of high school,” Patty added. “I think he had some type of hold on her.”