Amariah's invulnerable unless she chooses not to be and even a lethal hit would only delay her for a second while she torched; he can move her around, but not really damage her. That doesn't mean he couldn't pin her and make her life unpleasant, though; she pretends to need to dodge strikes, until a key moment when she doesn't, and she permits a blow to the back of her neck that pitches all her weight behind a dagger-thrust to his gut.

"Surrender," she suggests. This wound would kill a human, but not instantly.