If Anna would have been there, she would have DEFINITELY joined in the fight with Cale. Hmm...what's worse than having ONE prefect on your case all school year? Having TWO prefects on your case all school year.
Anna's proud of Cale! He's a hero in her book for standing up to them (even though she knows he feels bad about it at the same time).
Hogwarts better watch out: Mr. Prefect is out to get ya next school year!