Harry Potter and Rosalie Snape: Watching the Movies (MUSICAL)

There was a deafening bang.

Two middle-aged man and a woman was standing in the middle of the Great Hall, showing everyone (staff, ghosts and students alike) eight movies. Secrets will be uncovered. The future will be revealed. The fate of the Wizarding World will be decided.

However, those eight movies are those Harry Potter movies you have watched in the cinema or on your TVs. This time, a new character is added: Rosalie Snape, who prefers to go by the name Rose.

Who is this girl? Is she related to the Potions Master of Hogwarts? How would that change the plot of the story?

(The movie is a musical, the songs may be a bit weird because I'm not too good at writing songs. Most of them are based on other musical songs.)