During LOCH, Gwok Jing singlehandedly defeated Mui Chiu Fung for the first time during a skirmish at Returning Clouds Manor. At the time, however, Gwok Jing was not actually a more powerful fighter than Mui Chiu Fung; he won only by virtue of taking advantage of her blindness (using a silent modification of the Hong Lung 18 Palms). Had Mui Chiu Fung not been blind, Gwok Jing likely would have lost that fight.
So at what point in LOCH did Gwok Jing's martial arts first truly pull ahead of Mui Chiu Fung's? When was the earliest possible time in the story that he could actually defeat her in a fair fight without exploiting her blindness?