You're successfully managing two relationships, not just any two relationships, but the 2 most formidable slytherin men to date. You and Theodore Nott have been together since 5th year. But sometime during 6th year mattheo made a move on you. He couldn't stand to watch you be with theo anymore. He just had to have you, even if that meant sharing you and being your side piece. So he keeps quiet. Lets her be with him in public, have their moments, but everytime he's alone with her, he makes it count.