I don't know how she became your neighbor without you either sending an invite or accepting an invite from her.
But, you can delete her as a neighbor. At the top of the neighbor list is an "edit" button. Tap that and then remove whomever you wish. Be careful to tap it again when you're done, or you may delete neighbors you want to keep. (I've done this a couple of times.)
Delete her as many times as needed.