I hope things get better. If they do, it will probably only be because she refocused on somebody else.
If it were me, I would learn some simple new phrases I can easily speak over the headphones I was wearing:
“I want to be alone.”
“Leave me alone, now.”
“Do not touch my belongings”
“Never touch my horse.”
“I don’t want your help”
“Please listen to me. No means No.”
“You must respect my boundaries. I said no.”
“No, I cannot be your friend because you don’t respect my boundaries. I said I want to be alone, that you must leave my property alone, and yet here you are.”
These kinds of things, however, can be dangerous to say to these kinds ofo people, so it would depend on the adivce your counselor gives you. In general, though, I would make a few such statements to establish my personal boundaries and space, and there after ignore her and put my energies into protecting my property and pursuing my personal interests, no matter how she jumped up and down and stood on her head around me. I would stay at the barn if it were safe, but if it wasn’t, I would move to another barn if it would be safer for me and my horse.
I would also let the BO know what was going on. I wouldn’t ask the BO for help, because the BO might not be able to be recruited to my side, but I would simply inform the BO that I was being stalked, that her behaviour was dangerous, that I had taken a stand and made a few simple statements to her asking her to leave me alone. I wouldn’t at this time say I MIGHT have to leave. Only if the situation did not get resolved and the stalker continued, and I decided to leave, then I would tell the BO why, because of more incidents I had to leave. I would tell the BO that under no circumstances is she or anyone to inform this person of where I am moving mty horse to (she might find out anyway), and I would be careful to tidy up all responsibilities to the current BO so there were no loose ends at this barn when I left which would necessitate anyone having to stay connected to me at the new barn from the old.
it may well be that you can’t do that, but that would be the ideal to head for, if things do go south.
Good luck.