I would talk to her about moving him. He's going to end up hurt or hurt someone else.
My horse acted like this prior to me even leasing him. I worked at the barn he was at, and he'd run off all the horses protecting his woman.. who was equally @*)#&! and wouldn't let the other horses eat.
He got very stressed out because of this and tried this crap with us.. did not fly. And wound the rest of the herd up so the youngin's began to act study and claim their "mares" .. including a 3 yr old mare who claimed the 8 year old mare.. so silly lol.
We split them into two groups, separating Bonnie from Clyde and they both settled down and stopped picking on each other as much and the strange studdish behavior amongst the entire herd subsided and they were cool with each other again.
Since you have a choice in the matter, or at least some say, use it to your horse's advantage. IMOP.
"Strength is the ability to use a muscle without tension"