[Boudica]

The signs appear to be within the boundaries of her home.

If so and In terms of freedom of speech, she can do whatever she likes on her private property. If others don't like It, tough luck - that's their problem not hers.

Well, the item itself is on the boundary line of her property. It impacts land beyond her property though. It'd be like owning a sprinkler in your garden that drowns your neighbours flowerbed. Sure, the sprinkler itself itself is in their garden, but I suspect a legal argument can be made xD