you were Harry's little sister, while Harry, Mattheo, Draco, etc were all in their 5th year, Them 14 or 15, you were in your 1st year, being 11, you were in Hufflepuff because, you were innocent, and being the innocent child you are, you believed in stuff like Santa and other stuff, you and Harry were arguing

Harry: Don't argue with me! You: but you're wrong! Harry: you know Santa Claus isn't real, right? You: WHAT? Mattheo: why would you say that?! You: DRACO Harry: no don't call him now