Each time I ride my 5yo mare she goes absolutely brilliantly but when I stop her, more times than not she bends her neck round and touches her nose to the end of my boot. There's no other body language to back it up so sign of irritation or aggression she just touches it then turns her head forwards again as if it never happened. It is always my right boot. I have changed her girth, and even changed the length of my stirrups, I do not wear spurs just normal long leather riding boots and she still does it. We recently got a new saddle and bridle and she still does it? Help?