What you are describing sounds to me like high anxiety. A small amount of anxiety can be helpful when you take tests- it can help you focus during the test or push you forward as you try to study, etc.
However, too much anxiety, like what you are describing, is bad. You need to look at how much of this anxiety is coming from you/your family- sort of emphasizing to her that you must get a certain score or we can't pay for your college; that really may freak her out.
It reminds me of when my little one was 3 or so years old. He WOULD NOT poop in the potty! He pooped in his diaper but he wouldn't do it in the potty, no matter what. We talked about it, we read stories about it, but no poopies.
I took him to the doctor, kind of thinking frankly, that the doctor could somehow MAKE him do it.
The doctor just shook his head and said that my son "held all the cards (and the poop)." he said, he'll poop in the potty when he wants to- and he eventually did.
