I am not finding fault with your student's psyche, although it is interesting that you would see it that way. I am saying that for at least her previous art, she took tests, and a lot of them to get to yondan. So either there is something a LOT scariet about you, your teaching/testing methods, etc that she can't even get past one test with you, or she is not seeing herself as a beginner able to be no better than any other kyu student at her level. Whether either of you are willing to admit it, she has already proven that when she was a beginner in MA, she tested, and tested sucessfully. May or may not have enjoyed it, but did it. And now she can't. So it is not necessary to figure out how to get her over that fear, she got past it years ago. It is either you are much scarier, or she is not coming from the same place and self expectation she had when she tested before. I think she needs to be encouraged to see herself as she did when she was able to test, with no more expectation than her current kyu level out of either of you.