She finally winds down enough to notice his shock.

And blushes.

"Oh dear, I'm sorry. Here, you can have the pencil back."

...

"...oh. Oh! Sorry-- that must really make believing this isn't a hallucination a difficult prospect. I assure you, I've been doing it for quite some time and nothing's ever led me to believe it's a sign I've lost my grip on reality."

Cheerful, rather penitent Matilda.