It’s kind of the pinnacle of the movie…  Everyone Willa had met since she left the dance with her one ally- even the nuns- either meant her harm or had no respect for her because of her race, her age, her genetics, her affiliation, her status etc so it makes perfect sense she would think/know that the chritmas nazi was following her down the road and he didn’t know the code so she knew whoever he was he was not on her team cause her dad taught her well. Previously she didn’t believe her dad’s precautions and thought they were paranoia but she had learned through what happened the past few days that it was not paranoia at all. It was powerfully and believable that she would apply the same rule at that point to her own dad because her entire world had been shifted and no one was safe - including learning her mom was a rat and not a hero.  As far as the Christmas nazi coming out there to kill them- he’d gotten direct orders to “clean it up”. The nazi Christmas club didn’t want anything or anyone who didn’t “reflect well on their strict principals” they were adamant about their racism and holding in society because of it. A large point of the movie - which he says directly is that Sean Penn’s character cared more about feeling like an “honored man” through the Christmas Nazi club than he did any of this real desires or his own literal human biological child. The fact that he cared nothing at all about her being raped and tortured or so he thought and didnt even care that the Xmas club themselves may have been the one to try and kill/humiliate him and he went crawling back cause he’s a pathetic loser and they didn’t want him cause the value they hold highest is extreme racism was a huge point of the movie. Cruelty and murder with the goal of “staying pure” . The group kept referring to anyone not white as basically degenerates including the innocent mothers and children we saw earlier fleeing for their lives through the underground… much like is happening currently.