I have an 8 year old mare who has a little bit of a problem.
I have been her owner since the day she was born and the only one to feed her, groom her, and very rarely does someone other than me rides her. When I do put someone else on her she refuses to move. My friend who trains race horses and is very good at riding can't even get her to move, but when I get on she does just fine.
Why does she do this and how can I fix this problem?