I have another thought about who knows what.
When the boys head off to Bergamo, Annella invites both Marzia and Chiara to dinner. I imagine they all talked about the boys' relationship then.
When Elio returns, sitting in Annella's car, Marzia approaches him. She says something like, I'm sorry you're so sad. Then she says she is not mad at him, and can they be friends. "Pour la vie".
Thoughts?
Apropos a sequel. I'm not crazy about Luca's idea that Elio gets heavily involved with Marzia again. To me, the above scene precludes this. I'm convinced Marzia knows the nature of the boys' affair. She's already been hurt by Elio and has forgiven him. Move on, Luca!