Well if the teacher is asking question she hasn't presented in reading or in lecture then she is sadistic and setting her class up to fail. There is no reason to feel nervous about it because you can't prepare for what you cannot possibly know. So instead go over your lecture notes, re-read important pieces and bullet points. If there was other reading the textbook that she didn't assign, skim through it.

I'll give you an odd tip. My habbit in college was to read all of the picture captions, and other bolded captions in every chapter. I never studied for tests, I just would read all the highlighted and bolded pieces. I got As the whole time on all exams doing that. So, my tip is to go through any unassigned chapters and read the bolded points and picture captions. Then, let it be. There isn't anything else to do at this point since tomorrow is Thursday.