I don't like to think of myself as alpha or pack leader. I am a human. My dog knows I'm a human.
Your puppy is too young to be challenging anyone, and is probably just being a puppy trying to decipher all the mixed signals we as humans send them
Have you looked at NILIF? Do you take her to puppy class? What training do you do? Who does the training? How much is your boyfriend involved in feeding, grooming, training, walks, etc? maybe he's just a big play buddy to her, if he is not involved in these activities...