I get the distinct feeling that the mother is not nearly as "bad" as a surface-level reading of the story makes her out to be, perhaps because she herself has some form of trauma that she doesn't want her daughter to also go through. I guess we'll just have to wait and see.
Even if she has a legit reason to seal her powers away, which is something I am not really sure about, keeping it completely secret and not offering any sort of explanation still makes her a terrible person and a worse mother.
I think it's more as a pure yokai she doesn't get a lot of the reasons why humans do things or need certain things, and relied heavily on her husband to do so - as can be seen when she questions why humans put out offerings to the dead if it makes no difference - yet she still does it.
Still a bad mother but in the sense of not understanding rather than actively malicious.
Now it is completely understandable why she sealed her daughters powers, it was to protect her future partner to end like her dad, flattened under a giant woman
However the MC is both a giga freak and an uber virgin, so being it by cheer freakiness or avoidance he can survive getting pounded to death by giant cheeks, using the power of will or the power of cockblock
Ok, we are missimg something, where is the side effect what she recover her powers? She become a full youkai and not more intecteract with humans? She is controlled by the myth? She will eat childrens?
I have the strange feeling that the mom would reveal that having sex would cause some sort of weird curse on the guy and shorten their lifespans while her daughter will live as an immortal considering that she is regaining her powers.