Haha I had the same reaction with my two puppies. They are only six months now...but gosh how they have grown. In the four months we have had they they went from thirteen to forty-five pounds. They eat like little monsters.
Just guessing. She has the body of a heeler but a little longer. We also think she might have some sort of water dog because of the amount of webbing between her toes and the fact that water beads off of her.