Rick's right on this, in my view. It's fun enough talking about feuds with neighbours, but in reality they're just a pain.
Unless you're going to do whatever is necessary to win, there's no point getting in a fight; and those are the kind of fights noone wins.
Of course there could be an alternatve strategy. Maybe a temporary house swap with catspaw would do the trick. He could fix it that she'd welcome you back with open arms. That wouldn't be vengeance, just corrective therapy.
That could be a whole new philanthropic way of life for someone - going from town to town helping neighbours get on better by making them feel lucky they didn't have you as a neighbour. Social work รก la Incredible Hulk.