Lucy, my little chi/JRT mix, is agressive with other dogs she doesn't know. When we are walking and she sees another dog, whether along in their fenced yard, loose, or on a leash, she growls at them and raises her hackles. I try scolding her and pulling her back and praising her if she stops. She has continued this behavior, however, and I have ben having to limit her close contact with other dogs because I can't always trust that she will behave. Still, she usually listens pretty well, but in this situation she doesn't. What should I do be doing?