Neville

Despite your differences, you were in Slytherin and Neville in Gryffindor, you were very good friends. You were secretly in love with Neville. But something that kept you apart from him was that you believed in the Supremacy of Pure Blood.
One Saturday afternoon, you were walking through the Hogwarts grounds, when you saw Hannah Abbott arrive with her Hufflepuff friends and she approached Neville to talk to you, something that you didn't like since you two didn't get along (before meeting Neville, you used to make fun of her and her friends along with other Slytherin boys). You made a disgusted face when she approached and that made her leave: she looked at you angrily and told you that you would have to stop being so rude and left. You snorted and said "Despicable Mudblood" and that made Neville angry and he replied
—Maybe you're right, maybe you should change your ideas.
He sighed in disappointment and walked away, leaving you there. So you tried to look for him all day, but he kept moving away.
Until you saw it at dinner but I avoid looking at you