Why does she use "That’s definitely not", why not "That’s not definitely"? (I'm curious about the location of "not")
Native speaker’s answer
Rebecca
Great question. She is using "definitely not" to emphasize that she was not expecting what her sister said. So it is emphasising her certainty that her sister would say anything apart from that. "Not definitely" would mean you're not certain about something. So it gives the opposite feeling. Ex: A. Are you going to the party? B. I'm definitely not going. This means that B is certain they will not go to the party. Ex: A. Are you going to the party? B. I'm not definitely going. This means B may or may not go to the party. They are still undecided.