After three months.... I would definitely move out of there. They really should separate the aggressive horse/horses, but rather than even ask them to do that, I would move as soon as I could. I used to board, one place in particular had too many aggressive horses in one certain pasture, my mare was quiet and docile, kept to herself yet she kept getting picked on and one day she was run right thru the fence and hit a post and needed several stitches. I wouldn't even give it three days now, and three months is more than enough time. Time to move.