I don't know if it would work in this situation but I have heard of a method of showing a extremely dominant horse that yes, they may be in charge while you are gone, but ultimately, you are in charge. Put some feed on the ground(or wherever you feed her) let her eat for a second, and then chase her off. That's your food. Just like a dominant mare would if she wants the other mare's food. Walk off, mare heads back over, chase her off again. Don't let her have YOUR food. Repeat over and over again until she submits. Don't know if it would help with your situation, but just a thought.