He keeps waiting for her to run away screaming.
He knows that she gets scared when he uses, when any of them use. The black eyes, uncontrollable power, that scares her. Yet, here she is, by his side. It's hard for him to grasp how she can be near him, when she's scared of what he is. She stands by him, no matter what.
She's brave. She seems to good to be true.
That's why he loves her.