So she does get more unstable and sometimes causes problems but its not often and the plot focuses more on MC and his manipulation more than anything
HAVING SAID THAT, there is a disturbing spoiler that I will share so you know what youre getting into
Later on it is implied that she rapes the MC. It is a brief quick scene and never brought up again but that did make people uncomfortable.
I do think this is a great read with a phenomenal plot, but if youre not comfortable with this Ive heard the novel is better and not as kinky (take that with a grain of salt though)

They say this is good, I'm in the ch.32 but I don't know if I should continue or drop this. I like the mc and other characters but not the girl, she's so unstable. I don't have any problem with harem as long as the partner is good, not like that.