She called Kumugi "the best stepping stone" in the previous chapter, so she's well aware of what she's been doing. I am holding out hope that, while she's been consciously debasing Kumugi so far, she would find it entertaining or endearing enough that Kumugi now fights back that she would rethink her attitude towards her sister and become more supportive of herI hoping for at least a little twist in that her Sister is just that stupid rather than purely malicious. But its hard to say. Its getting harder to hope she ain't just a bitch tho.
Bet, I'm sure that bitch tempered with the light-bulb so Komugi would've never be able to light it up in the first place in order to gaslight her, that's why it overcharged