Yeah, I mean, she didn't really do anything wrong did she? Besides... I think it's valid that she'd be pissed to have someone suddenly pop up and get parachuted in a high position in the company she's been keeping up by herself. Even more so when she's been criticized and being put down at every turn by her gramps for being a woman. 
Even her concern about mc dating someone  way older than her is valid... I imagine the shock when he finds out who he is tho... tbf she's way more likeable that ml's sister when she was introduced.
It's overdramatic and the women pitted against women + misogyny can get tiring... but ch dramatic novels are my guilty pleasure...                                             

		
Idk i actually like curly hair