So looks like she's a combination of the various versions of the legend. While she did cause the death of her step-daughter, the axe still seems to have been an accident, based on her husband's reaction.
I actually cannot figure it out how the step-daughter died, it does not look like some sort of violent death, maybe it is from an illness?
It's my interpretation, too. Her stepdaughter fell ill, and rather than helping her, she kept doing the chores, letting her daughter die by neglect. This chapter was an oof in my books.
Based on the barely filled bowl and the legends about that specific monster, malnutrition.
The things you notice when re-reading a series. Like Miko being a fox foreshadowed in chapter 6. :D Always love it when an author manages to work in details like this that at first just seem like your usual clever bits to illustrate the situation, but in hindsight are the actual truth of the matter.
If you go back one page in that chapter and have a look at Miko's phone case...
So looks like she's a combination of the various versions of the legend. While she did cause the death of her step-daughter, the axe still seems to have been an accident, based on her husband's reaction.