I spoke to my sister in law a while ago - she has 2 girls and a new boy. Her middle child is 2 1/2 and you can tell that until recently she lived in a female-centric household:
To my brother in law: "Daddy is a very bad girl!"
To the dog: "Bob, you are a very bad girl!"
I hope she grows out of this before her little brother gets old enough to understand her - otherwise he's going to be a little confused ... :)