He knows she is changing. She almost became a person that he never knew all this time, and he hates it because it seems like it's hard for him to hate her now. Even his own mother liked her.
"No. Just because she lost her memory does not make her any different. She is still a Conrad and father even died because of her. That reason alone makes me unable to forgive her. " He was trying hard to remind himself this.
But his eyes started remembering his mother's face earlier. Even after he told her who Ariana was, his mother was not bothered by that statement. In fact, she wants to have a mother-daughter relationship with the girl, which Zayn really can't understand.
Does his mother know something he doesn't know?
He knows very well that his mother is not the one who can lie. So her happy face before is coming from her true feelings.
Creation is hard, cheer me up with some vote please! ^_^