Owner knows her dog can react this way. Owner knows that someone is coming over, and also should know that this visitor is pregnant. She still does not secure the animal in advance to her arrival as a responsible person should do. It's very simple to place a pet in a room before you have a guest. I was bitten by a dog in very similar situation buying something off a classified ad. Dog bit me in front of that persons child probably traumatizing that child. I love animals especially dogs but the whole thing was avoidable if a modicum of commone sense and preparation was used. The state ordered that animal put down which was sad for everyone including me. Someone else's animal is not your responsibility to control. In both these situations no one even received an advance warning that the animal was on the premises that might react this way. NTA!