@Samurai you just feel threatened regarding your ship that's why you hate her. And the fact that you hate her, either she do good or bad it doesn't matter. You'd see her in a bad light anyways. This often happens in romance, the other waifu candidate will get the hate even tho her character development was solid and her personality is good. Tho, i still can't say she won't do s*t but as of now she won't. If you think about it, isn't our MC the one who's acting weird no? He keeps himself getting affected by Noona. Noona didn't even do anything (for now). I think the author want to use Noona to make the Hae-in x YW shippers anxious to the point they could die without the intension of Noona doing something to mess their relationship. It's freaking effective tbh. Her presence alone already make you act like this. What more if she do something. It's kinda hilarious.
I don't care about your taste!