You also need to remember that nursing school tests require you to synthesize information, rather than just answer knowledge-based questions. You have to think about what the question is asking and apply what you know to the available answers (if it's a multiple choice exam).
I usually read the question and underline the key words. Then I think of the answer in my head before even reading the possible choices. As I read each one, I cross out the ones that don't apply, which usually narrows it down to 2 answers. Then I re-read the question again to make sure I'm addressing what is being asked. I find that doing this usually ensures that I'm understanding the question better than just read/answer. So far, this has worked well
You should also consider scheduling a time to meet with your professor to review the exam with her and discuss some strategies that would help you on the next one. Don't get discouraged. Take this as an opportunity to do even better on the next one!