The moment Crowley appears, Aziraphale feels a surge of relief, as well as some irritation and embarrassment at being caught in this position, and when Crowley strikes Illyria in the back of the head he only feels the clench of oh, shit. He pitches forward when she releases him, gasping, disappearing his wings immediately. He looks up to see Illyria advancing on Crowley, and Crowley has no idea what it is he's just accosted.

"Illyria," he barks, struggling back to his feet. He's not too terribly hurt, but he's still annoyingly shaky after that too-close brush with his wings. "Leave him be."