Zingy said:She's also a very submissive mare - well below the geldings in the pecking order and one of them is younger and smaller than her (and generally submissive to mares). So it could be a dominance thing where she feels too threatened for whatever reason. Got the same thing with one of my dogs where if anyone wants to say hello they have to kneel down as she hates people towering over her. So given May is only 11.2, adults are a lot taller than she is, so maybe that's the problem.
She is the most submissive pony I've ever met. Given that the only other time I had problems with her was when she did her eye in and was basically made to submit to treatment she found painful and stressful, it would make sense that the dominance thing is going to be an even bigger issue with her.
Don't forget as well that she has odd vision in that eye; so what might not ordinarily be threatening could well be a lot more so to her. Have you tried approaching from the offside? I did find that she was a lot happier about me getting on from the offside, presumably where her vision is clear and I was obviously me and not some cloudy shadowy threat she couldn't clearly see.