Why was scout successful in breaking the spell in front of the jailhouse

Even though she was told to stay away, Scout sneaks out to see what is happening at the jail. She sees the mob of men talking to her father and she runs across the square right up to Atticus. Once she is near him she tells him she thought it would be a fun surprise for him to see her there. The look on his face tells her she was wrong. She uses her childlike sense and innocents to take the situation in a new direction. She speaks politely and sweetly as she singles out Walter Cunningham and asks his boy. She reminds him that she is friends with his son an how he had brought her family hickory nuts,. She reminds him of the sweetness and innocents in life. She then carries on about Cunningham's legal mess and things get pretty awkward. He finally drops his guard and lets her know that he'll tell the boy hi for her. This diffuses the whole situation because Cunningham then has the boys clear out from the area.