You can't mess around with touchy feely stuff with a problem like this. I would carry a buggy whip with me and when she kicked at another horse she would get at least one probably two HARD whacks on the butt. There are times for gentle but this isn't one of them. Your horse could Kill someone. Please don't worry about her feelings or your bond with her. She can get over any harm that is done to her easier than a kid can get over getting kicked in the head.
She would get it from me with the whip.