Barn Owner's horse becomes aggressive towards my horses when around humans

My post clearly stated "month" not sure where the year came from.
Go for it, but like I said I don't want my horse thrown into a mixed owner herd. There isnt any need for it. Doesnt matter to me what anyone else thinks is ok for their horse.Why even risk or put up with the issues ? It's my horse and my money, I am the boss. I don't get all these posts here with spineless people that tolerate all kinds of crap from a business they are paying thousands of dollars.

Is the mare going after a horse or a human when it tries to bite? I read that it's going after a human.

The horse is taking advantage of the situation, that it can maybe dominate the horse being led. My horses will stand untied for the farrier but then the loose horse always wants to start trouble so he has to be tied or held. Common horse trait.

I *think* it was going after the horse, but the human got caught in the cross fire, if I understand it correctly.

Yes, it is going after another horse and the human is getting caught in the crossfire. All the other suggestions are good and have been considered, but in todays economy we are often trapped in situations that are less than desirable. We do what we can do? Move the horses? Can't afford to. Sell my horse? Who can afford to buy it? Like so many others we have real estate investments that we purchased before the crash that are now unable to sell, so we have several extra mortgages. So even with a 3 figure income in the family, things are tight.
So if anyone wants a beautiful piece of Ocean View property in the Pacific Northwest, I will gladly sell it to you and even build a house on it for you.