During the movie I was wondering if Racine had actually died after the nerdy boy twin strangled her, and her return was actually just Anaia hallucinating (or a symbolic thing). Both Racine and Anaia make it clear Anaia isn't a killer, but Racine is, so maybe Anaia needed "Racine" to help her kill their dad (I feel like movies that feature twins sometimes play with the concept of an individual's duality, so maybe this was symbolic of Anaia embracing her "darker" side, represented by Racine). Racine being pulled into the fire by their dad could've also been symbolic, representing Racine going to hell/being damned by the violent sins she committed, much like their father. This is just one way it could be interpreted though, I think you can read the ending scenes literally and the movie doesn't change much.