I new problem has come up with Amber that I am very unhappy about. Recently when we go on trail rides she has started trying to kick any horse that comes near her from behind. This all started when I began riding with a couple different horses that liked to bite her on the rump whenever their owners let them get too close . I do not ride with those horses as much anymore, and when I do the owners do not let them get close enough to bite. The other day I was riding with a friend who recently moved to a new barn close by and two of his friends from that barn. When the other two horses that Amber does not know would start to get near her from behind she would attempt to kick them (luckily never made contact), but if it was my friend's horse who Amber knows she never even thought about kicking. Having her kick out is completely unacceptable to me and I want to stop it ASAP, but I am not quite sure what to do. What I would like to do when she kicks or is about to is make her work harder and trot for awhile. Unfortunately we ride on narrow, rocky trails on a mountain, so there is no room to do this. Besides just staying in the back of all the horses, any ideas on how to fix this?
Oh, and on a side note when I took Amber to a show about a month ago she never made any move to kick. This was even with 20 horses in the class and quite a bit of crowding at the gate.