I do not think that the fact you have someone bullying you at work (and that is what it is) that should be allowed to go on. I suggest that you speak to the person and suggest that you and her speak to the supervisor together and also tell her (in a nice way) that the way she is behaving is adding to your stress levels and the cause of some of the mistakes you are making. I am sure she would not like to be told that she is causing some of these problems and that in the long run you are responsible to your supervisor. Making mistakes is not good and you could look at some ways, with which you feel comfortable, to reduce these and as someone else suggested the fact that you are looking at some improvements will stand you in good stead. I always find that if I have a problem I tend to stand back and think of ways of improving the outcomes. Good Luck and don't let anyone tell you that you are not worth the effort to try and improve. Ask your supervisor for some suggestions and try to work together without being in your face at all times as I am sure this does not help the situtation.