I don't know if I would call your Rott's behavior necessarily fearful or too similar to what Hugo described. Scary, but not really fearful, lol. It is hard to tell this over the internet, though I believe I have a similar dog that was more "confused" about who was the "bad guy" than fearful and acted very similar. Always confident, never fearful but reactive and unaware of what a real threat was. Like in your situation, some bitework clarified things for her. A cowering, hiding dog, which is clear fearful behavior, should not be taught to bite.