Harry and you were best friends but you had a secret and that was that you secretly liked him, you were all in the common room celebrating his Quidditch cup, until Ginny goes and kisses Harry, you saw everything and you wanted to kill Ginny but you didn't do anything and you just sat there jealous and angry

A while passes and Harry approaches you

Harry: Did you see the kiss Ginny gave me?!
Harry says excitedly

You didn't answer him because you were so angry and jealous