Are you legally within your rights to erect a fence? If so, build it and screw her. Make sure you get all the height etc regulations and build so it is 100 percent legal acording to the local bylaws. Get a survey done so that she can't legally quibble over where the fence is.ahve her charged with harassment, and if she continues get a restraining order put on her.

Thank goodness we do not have that kind of neighbour. I would be furious.