Okay, this makes much more sense now. The deviousness of getting her brother killed and her apparent idiocy are reconciled with this.
Huh...I didn't take note before, but the fact that there's an antagonist in this story separate from our host Su Luxia changes things a bit. Our MC has a useful weapon to point at the male leads, and events will tend to be more...violent.
LOL at this dipshit of a male lead though. "Your flirtation with this human vampire hunter will never work no matter how you shamelessly try to seduce him. Now let me send off my human lover who's a vampire hunter's sister. It's okay for me to do this despite having a fiance because I love her."