Teah Wimberly entered a written plea Thursday. She will be tried as an adult. If convicted, the 15-year-old could be sentenced to a maximum of life in prison.

Authorities say Wimberly and 15-year-old Amanda Collette were longtime friends who had recently stopped speaking before Wimberly shot her at Dillard High School in November. She then ran to a nearby restaurant, called police and confessed.

Her lawyer has said Wimberly may need medication after a psychological evaluation found she had mental health issues.

Wimberly also pleaded not guilty to a count of carrying a firearm on school campus.