Even though she was in tremendous amounts of pain from the burns caused by the extra hot tea, Moon Shadow's initial reaction was to attempt to dodge the pure white beam of light that shot out of Elric's mouth. It did not even register in her mind that he had said that he was going to use his dragon breath to heal her burns so that there would not be a single scar. To her it looked like an attack, and she would not have been understand how he was able to use dragon breath while he was in the form of a human, even if her head was not riddled with intolerable pain. So there was no way she could do so in the condition she was in.