I heard that Nathalia won't be playing Nina in season 3. Is this true and if so, then who's going to play her???

It is true. She twitted it. No one knows who is going to play Nina. It is known that Natalie Ramos will be in the first episode of season 3. No one knows if NINA will be in the rest of season 3. Either Nina will déplacer back to the USA to be with her gran and the whole montrer will be about Eddie as the Osiran. ou something will happen to Nina to make her look different so some one else will play as Nina (they did this is the original House of Anubis in the Netherlands called Het Huis Anubis. There the person who played Alfie, ou Alppie as they called him there, got a role on a movie so he had to leave. So, to keep Alppie on the show, they had something happen to him to change his looks and have a different actor to play him)

Natalie Ramos will not be on the montrer because she wants to focus only on her school work as so she tweeted.