Treatment ordered under this subchapter for a child with mental illness must focus on the stabilization of the child’s mental illness and on meeting the child’s psychiatric needs in the least restrictive appropriate setting. If the juvenile court or a court to which the child’s case is referred under § 55.12(2) orders mental health services for the child, the child shall be cared for, treated, and released in conformity to Subtitle C, Title 7, Health and Safety Code, except:
(1) a court order for mental health services for a child automatically expires on the 120th day after the date the child becomes 18 years of age; and
(2) the administrator of a mental health facility shall notify, in writing, by certified mail, return receipt requested, the juvenile court that ordered mental health services or the juvenile court that referred the case to a court that ordered the mental health services of the intent to discharge the child at least 10 days prior to discharge.