I speak from bitter experience.
no one can help until the person finds their own personal rock bottom. Unless they are willing to acknowledge that they are there... and then embrace help... your wasting your time.
Step away and be prepared to watch them die.
Held my brothers hand as he breathed his last... he never found his rock bottom.. some do, some dont. But never let yourself be drawn into trying to help them unless they have been there... otherwise you will find yourself holding that hand.... as it goes cold.