The tone in his reply hits her sharper than she would have thought; she can feel a rise in her own frustrations, but she holds back on snapping at him in return right away.

She's not stupid. Annabeth is the complete opposite of stupid, and she knows Percy Jackson better than the back of her own hand, and even if she has no idea what it is right now, there's something making him act like this, whether he's aware of it himself or not. Despite that, it still annoys her, frustrates her, because that's always been a facet of who they are; that doesn't mean she has to deal with it or him acting this way. Especially if he's speaking to her like that.

So she gets just as snippy. "You could keep hiding, if you're that comfortable in Cave Irritable."