Her denial helped make history (3)
I believe the answer is:
his
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for his that I've seen before include "To - Coy Mistress (Marvell)" , "that chap's" , "Belonging to that man" , "Belonging to the male" , "That man's" .)