Klaus doesn't think that there is anything beyond her words but actually processing what has happened, in part by expressing her dismay at the whole of it. So he just holds her, and kisses her hair, and tells her it's going to be alright (because he believes it), and that she's stronger than she thinks, and nothing can extinguish the light inside her.

Of course, he has no idea what she's thinking about, or he would amend that statement. She certainly can extinguish her own light.