She was angry that the teacher was bullied by others. How can I comfort her as a student?

If it's been a long time, you'd better not mention it. If it's comfort, don't mention it directly. After all, it made the teacher very angry. Then, you can say a few simple words of comfort, such as: teacher, don't be angry. Just be sincere. Finally, chat with her to make the teacher feel better and not angry. That's all.