eeeh all along is the elder sister that is doing it. She imagine
herself as the step mother.
The mother commit suicide in the cupboard, only to be discovered by
the Younger Sister, when then try to save her mom by pulling her
out, but the mom weight too heavy, the whole cupboard fell on top
of her, killing her together in the process. The Step Mother
Witness this but did not save her etc.
Since younger sis died, elder sis hallunicate that the step mother
is evil etc, n acutally she herself is imagining herself to be the
step mother.
