Diana IS her depression

What used to be a real girl back then in her life . .she becomes a monster now! Diana dies and probably the mother feels guilty over her death. Ad she was her only friend. She is depressed and Diana is a manifestation of her mind! And the kids know it! Diana comes back after she stops taking her meds?? She tries to stop her from taking them?? Why??/because no matter what u do u cannot stop depression it comes and goes... Just like the lights in this film. And endless circle of torture and pain