A 31-year-old Cheyenne mom has pleaded not guilty by reason of insanity to an aggravated child abuse charge alleging she threw her baby into a ditch.

Lillian Jeffrey entered the plea during her arraignment this (Thursday) morning in Laramie County District Court.

Jeffrey was arrested on Dec. 9 after Cheyenne police found her 2-month-old daughter (K.J.) lying in a rock-covered ditch at Love's Travel Stop.

Jeffrey reportedly told police that "all of her children are possessed by spirits" and that "K.J. was a demon and that she cleansed her."

K.J. suffered multiple skull fractures and a collapsed lung and had to be life-flighted to Children's Hospital Colorado for treatment.

Jeffrey's trial has been set for May 21. If convicted, she could face up to 25 years in prison.