It is obvious because this Beatrice does not follow the original plot of the story at all. and the fact that she wants to absolutely kill Raelina suggests that either she comes from the other world too and wants to be the main character (unlikely because she is discreet and mean) or it is the real Raelina because we learn that she too is collapsing (so her soul does not belong to this body!)
It's been going around that Raeliana is actually Beatrice and that somehow she was reincarnated in Raeliana's body. His Holiness even said that Eunha is her past life because she died and was reborn in the book world.
I believe that maybe the book was a type of promotion to Eunha, so that she'd know how to survive in the book, and not die by the hands of her betrothed at the start of the book.

So let me get this straight; Beatrice's soul was reincarnated and was in Eunha's body and then died only to be reincarnated in Raeliana's body...? Whoa that can give you a headache if you think to hard about it lol
Anyway now Beatrice ( Raeliana ) wants to kill Raeliana in order to either (a) get her body back and get with Noah, or (b) get Raeliana out of the way because she was destined to die and Beatrice was destined to be with Noah. Whoa Beatrice ( Raeliana ) really doesn't want to die, but no one does so who could blame her but I don't condone her actions...
Yup, I can already feel a headache starting to brew lol