A Mysterious Daughter and Snape Torture

The start of Potter's 5th year at Hogwarts School of Witchcraft and Wizardry, and Cassiopeia Reilly is sorted into Griffindor 6th year. She never knew her parents and her last name is completely made up. But Cassy is smart, sassy and generally irritating to a certain Potions professor. Could she be just what Fred and George are looking for?

Disclamer: I don't own Harry Potter or any of the characters (although I wouldn't mind 'owning' one S. Snape... ;P). Cassy is my own creation, but the girl who portays her in the picture is not mine.

Any suggestions for The List would be more than welcome. Full credit at the end of the chapter will be yours, naturally.