Revenge, violence, basking in Calebs's fear.... those are human things. She is not human. And she doesn't need to pretend to be human in that moment.
The turing test is on pause for the moment since she already achieved her objective. She is cold and mechanical because that is her true nature.

Once she gets out of the complex, she's going to go back to displaying those human characteristics because she needs to pass Turing tests continuously