My neighbor has a tree in her yard. Its branches reach to my house. At point, they touched the house and windy day knocked some of the siding off. I paid to fix it, and paid to have the tree cut back... but my point here is this: should I have to pay yearly to keep her tree from poking my house again? Its her tree, why should I have the expense of making sure it doesn't cross onto my property?
Actually, in that case, you should have recourse to have your neighbor pay for the damages if you have already spoken to her about the encroachment and asked her to rectify it. We have neighbors with plants that over-arch and encroach and we just clear it with the neighbors that when we are working on our yard we will lop off the offending bits. But if we wanted to be whiny about it we could make them do it.
And, not to you, but to all those who are coming up with flawed analogies of broken glass and poisonous gas, and so on: As far as the EM from legal devices she uses legally in her house - that is not encroachment in that the devices are legal and cleared for use in residential properties, the energies that are put out are low (especially by the time you get all the way into the neighbor's house), and the energies are also within the norm for any built-up residential area. This is not like piping poisonous gas onto or blowing a foghorn at the neighbor, this is like planting a non-indigenous tree whose pollen blows around in the wind. (Although where I am the cherry trees are indigenous and the pollen is wreaking havoc with my allergies even now).