You skipped it? She was bullied like Min Seol Ha. You judge her too much.
Just imagine if Eun Byeol was Ro Na and Rona was Eun Byeol... you probably would still hate the character of Eun Byeol since she knows how to play evil without being caught... And if Ro Na was Seo Jin's daughter she would be succcessful and stable bcoz she is fulfilling her dream... no need for her to pity herself or envy others. No need for pressure bcoz she is talented and motivated.