How do you get to Professor Trelawney's classroom?

Emma Thompson

Yes, she helps in the last battle. She throws crystal balls at the death eaters.

Professor Trelawney never predicted the "death" of any professor as Christmas breakfast. However, she did predict that Professor Lupin wouldn't be with them for long, and was quite right, since...

Meet with them privately and attempt to resolve. If that doesn't help, report their misconduct.

Hogwarts