I also agree, but would like to add that when I was watching, I had the belief that everything Kyoko was doing was actually planned by Nathan seeing as she seems to be completely following his commands. Throughout the film Nathan had shown he is willing to go to great lengths to fuck with Caleb, would making an android act strange be out of character? I was even sure Nathan was faking being drunk. So its already a massive risk to try save Ava who could just be playing with him all along, if he tried to save Kyoko as well there’s potential she sabotages their plans if she is actually doing Nathan’s bidding.

I can also understand why people came away from the film thinking Ava may actually be manipulating Caleb because she does not give a shit about any of the characters dying. She especially shows no reaction to Kyoko’s death, instead she is out acting like nothing even happened. A being who sees an enslaved comrade get murdered and doesn’t react is kinda frightening. I personally don’t think Ava was manipulating Caleb, but I’m not going to rule out that interpretation since the film does not.