You are Theodore Nott girlfriend, he's 'ex gf' was expelled from hogwarts 1y ago and they finaly let her come back, you where walking with him in the hallways when you saw her, they started talking in Italian (wich you didn't understand)

Theo: "squza, ti ho trattato come uno schifo quando stavamo insieme" [sorry, i treated you like shit when we were together].

Her: "non siamo mai stati insieme, Theo" [we we're never together, Theo]