After the "D-Stabilized" episode Danny freaks out and goes all overprotective. The problem is that even if Danny wanted to keep Ellie close to keep an eye on her he knows that he would't be able to keep her safe in Amity Park. So instead he gives her a portal gun and calls in his favor from Pandora to organize fighting lessons for her. Ellie falls in love with New Athens; so much so that she spends half of her time there and the other half in the human realm.
And then she decides to visit Greece. First she just investigates - tries to find similarities and differences between the Greece she knows and the modern one. She goes all in, learning everything she possibly can; the history, language, architecture, culture. And by the time she's been there for 5 months she realizes that this place has started feeling like home.