"The dialogue at times still feels like it could be written by AI… especially the part where the protagonist instructs his sister how to feel (to beg for life but not fight back) and she complies for the rest of the story as if she wasn't behaving totally differently a second ago."

Basically, she doesn't really want to die, but she also wants to make her brother happy. I just didn't do the best job conveying that and it makes it seem like a sudden switch in personality.