Western Literature mid-term exam

This week is the week of mid-term exam, and the first exam we met was Western Literature. Everyone has study harder than usual, and so do I. I had study my Western Literature through the night on Monday because I didn’t want to be failed again. I was in the classroom on time, but the professor was late, with no any examination paper, even the textbook. While all of her students were wondering what’s happening, the professor said she had to receive another very important professor, so she didn’t bring the paper, and laughing.
I know she’s a person who likes to laugh, but I don’t understand why she could be mad in just a moment. She was angry at the student who couldn’t hand in the paper on time. She thought it’s our problem, not hers. I know we have to do the time work outing, but when she said the words, has she thought about herself?