She is one bad day away from inpatient care and antipsychotics. Her parents should have noticed and had her referred to a psychiatrist already. Her brother is a stress-related mental health issue waiting to happen too, and her sister is a clear candidate for therapy.
Their parents, I assume, are either absent or busy coping with their own mental health.
Honestly I read this to see if it realises it is barely comedic and instead a fairly straightforward portrayal of borderline personality disorder with psychosis.