
What I get is that og!raeliana was poisoned by her husband, then the news reached og!beatrice so og!beatrice went back to investigate what happened to her friend, and that's when she met noah.
Then maybe og!beatrice reincarnated to korea, then read a book about beatrice amd Noah's story, then she was pushed off a bldg, died(?), then reincarnated back to the book's story, but in raeliana's body this time.
The og!raeliana should be dead so i don't know when or how she got the time to find the witch but since she was able to do this scheme, she must have found her way to that witch(?) one way or another then 'restar' their story again but this time swapped bodies with og!beatrice, so that she can have the good times (read: alive and happy with noah).
I haven't read the novel, so this is what i currently understand.

This webtoon has the same "author is god" theme like the Abandoned Empress. It is not clear, but it is presumed that the one who pushed her to death was the author because her soul is supposed to go to Beatrice. Her last wish in her previous body which is to pass the exams was granted to her in exchange of her soul going to another world. Some details are not clear, tho.
Our MC was supposed to be Beatrice (so she really was supposed to be the heroine), however because of the OG!Raeliana and her black magic shenanigans, OG!Raeliana swapped souls with Beatrice and our MC became Raeliana.