Despite the MC's hilariously overbearing internal monologues (they're so overblown I can't help but feel the author's just taking the piss), I've really been enjoying this. His/her victory over the house seemed earned by effort, intelligence, and persuading people who didn't immediately believe just because 'the MC is talking', not the result of some cheat power, and there were some missteps and setback along the way.
The overlap between the ruthless businessman former life and the stereotypical bitchy conniving oujo-sama behaviour is actually pretty funny. Seriously, if we were just watching the MC's actions from the outside, you could believe she was just another one of those vindictive scheming noblewomen who show up as villains in stuff like this, but she's just a lot better at it than her stepmother.