The woman in the fire decided that when the firemen got there, instead of letting them burn down her house, she would light the match for them.  She died for something that was very important to her.  Her impact on Montag's goal was to help him see that some people die for what they feel is right.  She played the role in the novel of a person who doesn't do the norm.  She was against the system.  Her role in society was, she made all the other people see that she would stand up for what was right.