Snohomish County Superior Court Judge Michael Downes told Mary Mazalic her actions were "stark proof of how low humans can sink," the Daily Herald reports.
Mazalic was convicted in September of child assault, criminal mistreatment and witness tampering.
The abused girl is the adopted sister of her boyfriend, 43-year-old Derron Alexis who is awaiting trial. She was sent to live with the couple in Mukilteo in 2010. She weighed only 51 pounds when she was rescued in August 2011 and is now living with foster parents.
According to court documents, the girl was suffering from severe malnutrition and had cigarette burns and "whip cord" injuries all over her body.
In the year the girl lived with Mazalic, investigators said she was abused her in a number of ways.
Mazalic often made the girl take off her clothes, then beat her with extension cords, a belt and even a piece of wire, all while gagging the girl with a squeeze ball or a sock to keep her from screaming, detectives said. These beating usually took place in the garage or the basement of the home, they said.
Mazalic often threatened to kill the girl, and even made at least one attempt to do so.
She tried to drown the girl by holding her under water in the bathtub, the documents said, and held a knife to the girl's throat and told her, "I'm going to kill you" to "show her she 'wasn't kidding.'" Mazalic told the girl she'd kill her and dump her body in a lake, and added, "I've done it before and would do it again."
The emaciated girl told investigators she was made to sleep in the bathtub in the basement of the home "hundreds of times," as well as in a tent in the backyard. When she was forced to sleep outdoors, she was not always given a pillow or a blanket, and the doors to the house were locked, she said.