Oh is that why Beatrice was helping Vivian?
only one body should stay alive, so Beatrice aka original Raelina need to kill the one in her body. That’s why she approached Vivian, in a way she’s not helping Vivian, but rather using her for her own good
It's more to,
As long as the soul that suit the body better exist in the same world, the body could never fully accept the soul.
In their case, Rae soul still exist (in current beatrice's body) hence Rae's body rejected Beatrice's (current Rae/Korean MC) soul. Hence og Rae/MC needs to kill the other to yeet the other's soul outta the world, so that they could take full control of the body by being the most compatible one(since their soul is already in the body hence nearly assimilated already).
i just realised that the MC (korean girl) was supposed to enter Beatrice body and become the MC in the book, but before she could get in the body the ori Raeliana took it first, so she went into Raeliana body instead
So in the end, she is Noah’s girl through and through. Either as Beatrice, or Rae or her own korean body!!!!
damn im so slow