Meriwether County sheriff Steve Whitlock told the Atlanta Journal-Constitution Thursday night that the 12-year-old boy told his teacher about the killing. The teacher reported it to the Division of Family and Child Services, who contacted police.
The pet's death allegedly took place at the family's Warm Springs home.
Whitlock said 38-year-old Lynn Middlebrooks Geter faces one charge each of animal cruelty, child cruelty and battery.
He said she was arrested last week and remained in the Meriwether County jail Thursday evening. It was not immediately known if she had a lawyer.
Meriwether County is located about 90 minutes southwest of Atlanta.