Wow what a long thread. Some pretty funny comments in here.
There is really not much you can do about it other than keep doing what your doing. Either they will eventually get it or they won't. When the cops come just be prepared keep track of the officers names you have spoke with previously then make darn sure that they go tell the neighbors you are doing nothing wrong. As long as you are good with the rest of the neighbors and they have a clue. one of them will eventually tell the nosey neighbor and they will stop.
I had an old neighbor like that once before. When her husband died she became the nicest person on the block where as before she was pretty much a witch.
Ohh one more thing if the cops do come tell the cop that you want an apology from the neighbors when the LEO goes and talks to them. that will at least give them some humble pie