While we have already noticed this during the Season premiere, and discussed how Sansa has become a newfound Cersei admirer, a new thing I came across in this article was a quote by Sophie Turner:
She's a very silent character . . . you don't really know what she's thinking. The only real way we knew what she was taking in and learning from these people [is] because she would mirror Cersei's hairstyle or Margaery's hairstyle. . . . It's really interesting to see that sort of physical representation of her adapting to each situation.
(Not) looking forward to all the evil Sansa is about to unleash on the Winterfell now that she's in charge!