Sammantha Allen, 29, from Phoenix, was convicted of first-degree murder and four counts of child abuse in relation to 10-year-old Ame Deal.
Authorities said Allen and her husband, John Allen, made Ame get into the clear plastic box as punishment for stealing an ice block. She was left in the box and found dead six or seven hours later.
John Allen's trial is due to begin in October. He's also charged with first-degree murder and child abuse and faces the death penalty.
Sammantha Allen will become the 55th woman sentenced to die in the US.
It's been reported that Ame's death occurred after years of abuse in which she was forced to eat dog feces, was kicked in the face and beaten with wooden paddles.