She's not bucking, she's kicking out. Big differance. That mare is not having fun, not enjoying going 'round and 'round in circles, is frustrated and bored. It's written all over her body. I have 4 horses right now that the owners have come to me to help with here, and every one of them had the exact same problem. They are mentally fried by the arena and bored to tears. We took them out, are going on some very long, diverse relaxing rides and putting fun back in their lives. They are doing great. It does wonders for attitude, fun does. Isn't that why we got into horses in the first place? Fun? And not just our fun, but theirs too?
You may already trail ride, I don't know, but I would balance what you like to do on horseback with an equal amount of whatever it is she likes to do. That's what builds a partnership. Give and Take.
PS - I apologize if sometimes my posts sound almost a little too ...lecturing? I don't mean it that way. I have 7 children of my own that I have taught/am still teaching horsemanship, plus clients over the years. I'm just not always sure how to communicate thoughts on a keyboard and computer without it coming across as the "Daddy" I am. I don't wish to offend.