Shawna Gatto, 43, was arrested by Maine State Police detectives Thursday and charged with the murder of Kendall Chick, 4.
The Maine State Medical Examiner's Office told detectives that Chick died from a blunt force injury to the abdomen .
Gatto is the fiancee of the girl's grandfather Stephen Hood, 53, with whom the child had been living with for nearly two years.
The decision to charge Gatto was made following a meeting between state police, the attorney general's office and the state medical examiner.
Gatto is being held at Two Bridges Jail in Wiscasset.
Her first court appearance has not yet been scheduled.