Poor Abigail, she is trying so hard and must be feeling very disappointed. I do feel for you both.
Like everyone else here, I think groundwork could be the answer and I'm sorry that the owners have a confrontational attitude towards their horse. Would they allow Abigail to do groundwork with him for the time being, so that they can develop a relationship and he begins to understand that she counts as a grown-up and needs to be attended to? Groundwork can be so much fun, and both horse and handler learn a lot.
Like everyone else here, I think groundwork could be the answer and I'm sorry that the owners have a confrontational attitude towards their horse. Would they allow Abigail to do groundwork with him for the time being, so that they can develop a relationship and he begins to understand that she counts as a grown-up and needs to be attended to? Groundwork can be so much fun, and both horse and handler learn a lot.