My mare lunges fine in each direction and is fine when riding in an arena counter-clockwise but when we change direction and go clockwise, she is hesitant, puts her hind end in the middle of the arena and side steps, just won't go straight along the rail. My friend pointed out that her vision may be compomised in her left eye and she can't see rail very well (or at all) and is apprehensive about her left side and what might be there. Sh will stand with a gate or rail on her right side but not on her left side.
Since your mare has vision problems in her right eye, along with her past abuse, may be the reason she does not like going counter clockwise. Something to think about and have checked out when she sees the vet