A nurse who pleaded guilty to evidence tampering in the Kelsey Berreth case was reportedly scared of the man who has been charged with her murder

• Colorado mother Kelsey Berreth was last seen on Thanksgiving.
• Her fiancé, Patrick Frazee, was arrested and charged with first-degree murder in December.
• On Friday, Idaho nurse Krystal Lee Kenney pleaded guilty to tampering with evidence in the case.
• Kenney's close friend told CBS News that the nurse had known Frazee for 15 years and alleged the nurse was afraid she would be killed if she didn't help him.

A nurse who pleaded guilty in connection to the case of missing Colorado mother Kelsey Berreth was apparently afraid of the woman’s fiancé, who has been charged with her murder, a friend told CBS News.

Berreth, a 29-year-old flight instructor, disappeared on Thanksgiving. Patrick Frazee, her fiancé and the father of her 1-year-old daughter, was arrested in December and charged with first-degree murder and three counts of solicitation of murder.

On Friday, Idaho nurse Krystal Lee Kenney pleaded guilty to tampering with evidence in the case.

Kenney's close friend, Michelle Stein, told CBS News that the nurse told her she helped Frazee try to cover up Berreth's death.

"I will just tell you Krystal was very, very scared," Stein told CBS. "Krystal's a very level-headed, kind, fun-loving, happy-go-lucky person. She's a tough cowgirl. But she was absolutely scared and extremely upset."

Kenney and Frazee previously dated and have known each other for 15 years, Stein told CBS. She would not confirm if Kenney and Frazee had a sexual relationship.

When CBS News correspondent Nikki Battiste asked if Kenney was fearful of Frazee, Stein said, "Yes."

"She did tell me that she has never seen this kind of evil in anybody," Stein told Battiste.

When Battiste asked, "If she didn't comply with Patrick, he might kill her?" Stein replied, "Yes, that's what I believe."

In a court plea on Friday, Kenney said she had disposed of Berreth's cell phone two days after her death. Berreth's body has not been found.

"I had no right or authority to move the victim's cell phone," she said during her court plea.

Read more: Crews plan to search landfill for clues in the disappearance of Kelsey Berreth, who investigators believe was murdered in a plot orchestrated by her fiancé

Stein said she had "absolutely no doubt" that Kenney wasn't involved in Berreth's murder.

Kenney faces up to three years in prison. She agreed to testify against Frazee at his trial.

Frazee is currently in jail without bail. Police believe he murdered Berreth at her home but have not determined a motive.

Berrreth's phone last pinged near Gooding, Idaho, three days after she was last seen in November.

Frazee is also accused of trying to find someone to kill Berreth three times between September and November of last year, according to court documents obtained by Denver 7.

A preliminary hearing is scheduled for February 19.

• Read more:
• The fiancé of missing Colorado woman Kelsey Berreth has been formally charged in her death even though her body hasn't been found
• Fiancé of missing Colorado woman Kelsey Berreth is arrested on suspicion of first-degree murder
• Police are executing a search warrant at the home of a Colorado man whose fiancée went missing on Thanksgiving

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