Samara left after some harsh remarks not caring about anything that happened to Talia. She had already considered her as a lost specimen whose only job was to exist in case the coan needed her in the future.
Ariel watched her leave, gritting her teeth in frustration. Samara has always been cruel but this time, she crossed a line. But after thinking about it, she crossed it years ago, maybe before she was born.
Experimenting on people, causing them to suffer excruciating death have been going on for who knows how long in this facility.
Most of it's inhabitants have long since became numb to clan's practices. Helplessness might be the prime cause but since they began to accept it, they were just as guilty as Samara.
Maybe her humanity surfaces because Talia was related to her, seeing her in that state really stirred up emotions that she had long since forgotten.