Updated

A San Diego girl who admitted beating her adoptive mother to death with a claw hammer when she was 14 has been given 16 years to life in state prison.

Sixteen-year-old Heather Marie D'Aoust was sentenced Wednesday in Superior Court.

Prosecutors say D'Aoust, who has serious psychological problems, stuck her adoptive mother at least 15 times with the hammer in the kitchen of their Scripps Ranch home in May 2008.

Rebecca D'Aoust, 56, died at a hospital.

The girl had argued with her mother a day earlier. An FBI agent testified that the teen's cell phone had a text message about her plans to kill her mother.

The teen pleaded guilty last month to second-degree murder and assault with a deadly weapon.