you we're mattheo riddle girlfriend. One day you we're outside in the Hogwarts backyard with the Slytherin boys ( Regulus,Theo,Lorenzo,Tom and of course Mattheo your boyfriend) when you started talking to Cho Chang when she said

Cho: I'm not Mattheo's friend! I'm his lover. she said confidently

You: What? I look at Mattheo

Mattheo looked at your you could see in his eyes he was somewhat sorry*

You: You cheated on me with that? I say and gasped dramatically

the Theo, Lorenzo and Tom laughed a bit. Mattheo rolled his eyes and Cho looked confused