Sheena Cornwell, 28, of Des Moines, told police she killed the dog, Lilly, a 15-year-old pit bull mix, because she "was going to die soon anyway."
Joshua Vandyke, the woman's boyfriend, said Cornwell was annoyed because the dog would often pace back and forth in the house, but he never thought she would kill the animal, ABC News reported Monday.
He said when he got home Saturday, he found Cornwell angry at Lilly. Cornwell then took the animal in the garage, hanged her from the rafters by her collar and waited in the garage until she was dead, WOI-DT, Des Moines, reported.
He told police Cornwell had a drinking problem and was drinking vodka the day of the incident.
Des Moines Police Department spokesman Sgt. Jason Halifax said Cornwell had no previous record of animal abuse, and if convicted she could face up to two years in prison and a $6,250 fine.
Vandyke is attempting to get a restraining order against Cornwell. He said he fears for the safety of the other two dogs the couple shares, ABC News reported.