A 15-year-old Saskatoon girl accused of lighting a high school classmate on fire in September is facing two new charges.

The teen is alleged to have uttered threats and assaulted an adult in November, while she was in custody. She remains behind bars.

The 15-year-old injured in the fire incident remains in hospital.

The accused, who was 14 at the time of the alleged fire attack, is scheduled to return to court Dec. 18. She cannot be named under the Youth Criminal Justice Act.

The Crown gave notice at an earlier hearing that, if the teen is convicted, it will seek to have her sentenced as an adult.

The defence applied for an assessment to find out whether the girl was not criminally responsible. Judge Sanjeev Anand granted the request to assess whether, at the time of the alleged offence, the teen was suffering from a mental disorder.

Under questioning by Anand, court heard that the teen had been under the care of a nurse practitioner and had been diagnosed with a "psychotic disorder." She had also been admitted to hospital this past summer for emergency psychiatric care.