
If you guessed this of your own without reading the novel then you're a genius. You're actually pretty close to the truth, just add in a few more pieces and everything is solved.
If I remember correctly the real Raeliana wasn't dying she was just obsessively in love with Noah, and jealous of the real Beatrice and so she used black magic to switch places with her but it backfired

This was a way better theory cause my theory was the real Raeliana got switched with the modern day MC and is going through university totally freaked out abt modern day academia.
And then Beatrice just went crazy for some reason because her real best friend is gone. I dunno. Never put muchthought into it hahaha
From what I have read so far it’s seems like the real Raeliana find out she was going to die and used black magic to switch Beatrice and her (Raeliana’s soul). So the current Beatrice is really Raeliana. I think our main character was always meant to Beatrice but since the black magic interferes she was switched to Rae’s body and regained her memories of her past life. If my theory is true that will explain why even tho Rae escaped death she is still dying and why Beatrice is also dying and plotting to kill the main character. The cost of the black magic was one of them has to die.