I voted "not sure". I am 100% certain that Tori wouldn't. I don't have a clue if Katie would or not. I would like to think she would. I think if we were outside and someone came up to me in a menacing way that she would be protective. I have always wondered what she would do if someone came into the house without my knowledge. I really think she would just wiggle and waggle all over them and be wooing the whole time...lol. Now, if Katie were to be protective and attack someone, Tori might help out her big sister. I hope I never have to find out. Just having Katie is enough protection though. People are scared when they see her and sometimes of Tori also.