So what? You expect her to be the baddest bitch in town after she suffered through years of emotional and physical abuse? Her own sister even turned against her. She's been "worthless" her own life. Most of those stories like "I'm going to get revenge!" immediately right after the introduction are completely unrealistic. She needs time to heal, feel loved, and take care of herself and realize that she's worth so much more.
Anatol and Princess Agnes really help in that factor, but Riftan won't know what her father did until 2 years into their marriage or so.
Seriously, it's a chance that the ML is hot af because the FL is soooooo weak it's frustrating