Canaria is oblivious to his love because she's been living this entire new life under the impression that he will one day abandon her. From what I understand it doesn't really matter how smart someone is, if that person has already established an idea as fact in their head they'll have a hard time noticing subtle hints that suggest otherwise. Therefore, they need to be told directly that their understanding is incorrect or they will continue to misunderstand.
At the very least, Canaria knows Cesar doesn't hate her anymore, but she thinks that he simply tolerates her or, at best, thinks of her as a potential friend. She has no idea he's in love with her because of her preconceptions blinding her to the truth. Seriously, fuck those fireworks for making things worse.