I just want to reinforce that she already has it in her head, she has established dominance over you.
Once you firmly establish you are the herd leader, you may never be able to totally relax in her presence. You might always have to have eyes in the back of your head so-to-speak.
Not all alpha dominant horses behave that way. Mine never has but, the bully who is third in the pecking order and wishes he was first, does.
He's been in my herd 16+ years and I still can't trust him 100% if I don't have the buggy whip (an extension of my arm) with me when I open the paddock gate to let everyone out.
Little-by-little he will gradually walk closer to me until he would be pushing me to open the gate so his Legend-In-His-Own-Mind-Self could hurry into the pasture. He freqently gets poked in the chest or wailed alongside his neck with the buggy whip because he is a horse who believes in "better to ask forgiveness than permission" but all he gets is pushed back by me
I understand your situation and what would happen to the horse, ultimately, were it not for you. As long as you are an assertive person, things should work out.
What about vets? In case of emergency, do you have a veterinarian in your area?