Sirius Black

You are the daughter of Sirius Black's younger brother, Regulus Black. Regulus died when you were 6, now you are 7, and you look like your father. You live with your mother's older brother, Ella Rosier, that was your mother's name, and her older brother, Evan Rosier, that is who you live with.
You wanted to go to Hogwarts and you did at the age of seven, just by your wits and without wand magic. You were in Slytherin.

There was a ball in honor of the holidays and you were there too (you were in your first year) suddenly Sirius (he became a professor at Hogwarts, teaches defense against the dark arts) and his godson "Harry Potter" came up to you
Sirius: Hello young lady. You are my little brother's daughter, aren't you? And what are you doing here so late?
Harry: Godfather why did you go to her? It was 00:56

(Also, you had an enemy, "Harry Potter" he was a popular boy and Sirius' godson. Harry hated you because you were his blood relative and he was not)