"How do I know it's not a trap?" It's obviously a trap. This old bat continues to yank your chain, force you to almost kill your beloved sister (twice), and you're just thinking "Yeah, I should just do what she wants me to do!" How GD stupid can the MC be? From what we can tell both mother and aunt completely think that Bai Ji is just kind of broken because she doesn't turn her back and humanity and fully accept her identity as a vampire. This is obvious, and yet Bai Ji keeps complying with them.
Edit: I lose track. Yanna is a Patriarch pawn? How does that make sense? (And I have a hard time telling the vampires apart.)