I would absolutely contact police, describe the situation and ask what options exist. (This is especially easy for me to say because one of my relatives is an officer, so I can bring it up in casual conversation.) Don't wait for the next incident and call 911; call the non-emergency number or a community/neighborhood officer if your municipality has one. If this dog has no problem running up to and intimidating another dog, what might it do to a little kid? Before you contact police, write or type out a rough timeline of your observations, especially the bit where you asked her to control her dog and she refused/told you to walk your dog somewhere else, then you stated your intent to carry pepper spray. Document, document, document, because your neighbor sounds like the type who will deny, deny, deny (and perhaps sue, sue, sue if it does come to your having to use pepper spray on the dog, in defense of yourself or your dog). If for some reason you don't get a cooperative response from police (which I hope is unlikely), reiterate that this person told you to walk your dog somewhere else, and calmly ask what is reasonable about that. Get the name of everyone you talk to so you can follow up if needed. Walk your dog somewhere else? That is seriously outrageous. Take this action not only for yourself, your dog, and anyone else in your neighborhood who might be threatened by this dog, but for your neighbor (whom you might save from a lawsuit) and the troubled dog itself. Maybe the best case scenario is the neighbor loses the dog and the dog gets a new lease on life with an owner who actually has a conscience. Good luck, and let us know how it plays out. Obviously this has my dander up.