"The hero and the villain are having a Sword Fight or similar one-on-one altercation.
Meanwhile our lovely heroine, who the narrative will insistently claim is physically capable, is just standing around... and doing absolutely nothing. This isn't a case where she's trapped, incapacitated, physically impaired, or any less experienced than the hero, himself. This is an able-bodied woman with some established ability who is just standing around on the sidelines, helplessly watching while the men do all the dirty work.
So no trying to improvise to assist the hero. No calling for help. No making any attempts to stalk off while the villain is distracted; anything that could possibly enable the hero's success. Not even cheering the hero on to boost morale. You could replace her with an inanimate prop for all the good she's doing.
The situation doesn't necessarily have to be Hero vs Villain. It can also apply between good guys, especially in terms of romantic competition. The point is that the girl is still not helping either of them nor doing anything to stop the fight, not even by saying something that could settle everything between the combatants."