There are few things so frustrating as having a full bucket of milk kicked over, just as you are stripping out those last few squirts, and dreaming of the yogurt, cheese, or just plain creamy milk you are going to enjoy. Even worse is when she kicks you in the nose first, then plants her dirty foot squarely in the bucket. A kicky milker can cause all kinds of problems, and be downright dangerous. Frequently, kicking is only a symptom of other issues, such as extreme nervousness.
A nervous cow is a dangerous cow.
She is liable to hurt herself and other cows or people. She may try to jump or charge through fences, and likely will attempt to break out of the stanchion if she is frightened. This is not an article dealing with nervousness, but I will say that the cure, so far as I have experienced, is twofold: 1). Lots of gentle, but firm handling, feeding of treats, and desensitizing her to common things she perceives as threats.
2). Feed lots of dolomite. Extreme nervousness may be caused by a magnesium imbalance, which can usually be corrected by feeding dolomite.
Here are a few tips I have learned from several years of milking cows; our own and others. Several were first fresheners (who usually kick a lot), and a couple were just plain kicky (belonged to friends).