The mother just gaslighting Shinwoo's emotion. Then the stepdaughter come just to make it 'clear' that the mother is suffering.
The twisted plans is to let the mother let go her burden emotional mental health to be a normal-non problematic mother.
So yeah, idc whatever happened to her, I just wish she gone from the plot. She is the reason Shinwoo has a lot of undone knot with his feeling.
What happened to shen Yue ? I missed him already