She didn't even know he was an enemy, she just punched him because he was shady looking.
I mean YES, he was an enemy, but not hers? She was just clearing a path for her friends dad. Not defeating the whole wave of monsters. So why did she punch a random guy that could have possibly been a random citizen AN INJURED one at that. Because he spat blood. Not much of a hero, is she? Decking injured old people in the middle of a monster-filled forest.