The depiction of Elizabeth I is interesting, because it plays on the audience’s expectation. On the surface, she begins the episode as a caricature, a natural prequel to her portrayal in The Shakespeare Code and jokes preceding The Day of the Doctor. But underneath her more jaring characteristics, she truly shines - not only is she perceptive and witty, she is brilliant strategist and leader. To underestimate her is a grave mistake.
The line “I may have the body of a weak and feeble woman” is lifted nearly word for word from a speech given by the historical figure. In it, she continues: “…but I have the heart and stomach of a king, and a king of England too.” [x] Taking up arms and slaying the Zygon, demonstrating quick thinking when she decides to impersonate her own duplicate, providing the Doctor with a potential escape and ultimately figuring out the Zygons’ entire backstory and plan - Elizabeth is certainly shown to fit this description.