"You're showering with me, then?"

Instead of arguing that she's lost her appetite, she picks at her sandwich a bit more. He wants her to eat so she can maintain her strength, and she doesn't want to make him worry anymore than he's already doing. So she eats and she teases him, laughing a bit as she does. That of course makes her wince, and she's very careful to keep from giggling further as she slowly swallows a bite of sandwich.