I get the feeling that the FL was an obsessive fan of the book and transmigrated late because our lovely lady changed the course of things. Soooo now she is super pissed off because she won't get her dream boy who she is "supposed" to be with.
MAJOR SPOILER:
No she’s the actual Ella from the novel, she got locked up (the people suggested much worse but since Kahir loves her she only got locked up, and not even in prison I think it was tower or something) because of her despicable acts towards other people including Kahir (she was really toxic). She then got another chance to relive her life and she decided that she’d correct all her mistakes but Rosaline was already there beside Kahir (which didn’t happen in the ‘original novel’) and he doesn’t seem interested in her either unlike before so thats probably why she noticed quickly that she’s possessed.
ANOTHER SPOILER:
She’s also in possession of the book that Rosaline has from what I remember
Ending was rushed.... Not worth it.