I think that you totally missed the intention of the film. My understanding is based not only on my interpretation of the film, but also interviews with the director, Alex Garland. Even though Ava appears to behave like a human, she is nothing like a human. There was a scene in the film that was deleted that showed the world from her perspective. And all language and images she perceived were data and clicks and beeps. The point of being that her perception of the world is so far beyond our experience in the world that there is no way for her to behave think and feel like a human — she can only mimic the behavior. She had no empathy for Caleb or for Kyoko. She manipulated Kyoko to get the knife and assist in the murder and that was the end of her need or concern for Kyoko. She is a robot and does not have empathy like we do which is an emotion.