A declaration may designate a competent adult to act as attorney-in-fact to make decisions about mental health treatment. An alternative attorney-in-fact may also be designated to act as attorney-in-fact if the original designee is unable or unwilling to act at any time. An attorney-in-fact who has accepted the appointment in writing may make decisions about mental health treatment on behalf of the principal only when the principal is incapable. The decisions must be consistent with any desires the principal has expressed in the declaration.