Our guard dog

We had Barbie since she was a 2-month old puppy. She was given to us by our vet whose dog gave birth to 2 white puppies. Being the youngest and only female of our 3 dogs, all attention was given to Barbie. Do you think Barbie would be a demure dog?

When she grew up we noticed that she was getting ferocious until she developed the habit of barking at people passing by in the street. Now she is like a guard dog. Even staying inside the living room Barbie would be looking outside for a potential enemy. Indeed she is our little guard dog.