It was a self-feeding loop: Verity laughter setting Sally off and Sally's laughter setting Verity off. For the life of her, Verity could not stop laughing. She was laughing and cussing and thrilled with life.
"Yes!" she all but shouted between laughs. "Yes, we totally do! We should owl Titania right now and tell her to send lots more billiwigs!" She gave Sally a sloppy kiss on the forehead and then laughed harder at her expression.