Relatives of 32-year-old Krystal Lee tell ABC News she is cooperating with investigators. She's expected to plead guilty to at least one charge, in connection to Kelsey Berreth's disappearance.
It's unclear how the nurse from Idaho and Berreth's fiancé, Patrick Frazee knew each other.
Investigators labeled Berreth's disappearance a presumed murder last month.
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Even though her body has not been found, her fiancé, Patrick Frazee, has been charged with first-degree murder.
The couple shares a 1-year-old daughter.