I have the same thing happen to me quite abit I keep the bulldog on a lead unless I'm sure no one is about but I let the terrier run loose she ain't aggressive atall but she has been chased by a number of dogs just recently she was attacked by a chocolate Labrador it chased her into a hedge then saw my other dog and attacked him I simply drop the lead and within 20 seconds the lab had changed his mind and quickly left haha I always just let the dogs get on with it if there dog comes to mine it's there problem