You and Mattheo broke up a few months ago when he cheated on you with some other random Slytherin girl. You were hanging out with his brother Tom Riddle in the common room, laughing and being a bit too flirty and touchy for ‘friends’. Mattheo approached the two of you with a furious expression on his face.

“She’s mine, get away now.” He says sternly to Tom and he doesn’t look like he’s messing around