According to reports, a caregiver at the retirement home in Chézy-sur-Marne in northern France, found the victim dead in bed on Saturday, shortly after midnight.
The victim's face was severely bruised, and a post-mortem examination revealed that her death was caused by "strangulation and blows to the head."
The 102-year-old suspect was "in a very agitated state, confused and told the carer that she had killed someone," a prosecutor said, according to BBC.
The suspect is currently undergoing psychiatric tests to determine what state of mind she was in during the murder.