I'm looking for a book, that i read five or six years ago

[Irish]

I'm looking for a book, I remember that the heroine falls in love with a boy I remember that it was an immortal creature but I don't remember which one, I read the book years ago and I don't remember it well, however, while the two of them begin to fall in love, another girl ex-girlfriend comes out or so she says she is, to be together she has to make a choice, that is to be transformed like him, that she did not accept, which she later discovered and it almost killed her, reason why he had to erased her memory, I do not remember the story well, but in the end it turns out that she can not be transformed in what he is, because her soul is incomplete, and it turns out that the woman who appeared earlier is an old incarnation of her ( and so she is the part of the soul that lacks her ) and when she dies, the girl's soul is completed and she can finally be with the boy. It should be a single volume, at least it was when I read it.

[Karen ⚜Mess⚜]

Hey Irish,
If you don't find your answer here try this group
https://www.goodreads.com/group/show/...