This is christez. Just too lazy to keep switching back and forth between journals.
A half-blood is good, but maybe her mother was from a wealthy/noble family. Living well could be the only thing they would have in common? Everything else sounds good. Constantly butting heads. Always in disagreement, and that opposites attract thing that they are both fighting. At least the step-sister is in constant battle with. Ever since they found themselves at Beauxbaton.