Ember hatched prematurely and was frail as a result. She was small and sickly, but her father was expected to show her off to his subjects. To avoid rousing suspicion, he did so as though nothing was wrong. His enormous claws tricked dragons into believing she was a normal-sized hatchling.
Torch acted aloof toward his daughter, charging his wife with caring for her until her health improved. Being overly involved would only make dragons question his authority and paint a target on the princess’ back.