It was gratitude; gratitude, not merely for having once loved her, but for loving her still well enough to forgive all the petulance and acrimony of her manner in rejecting him, and all the unjust accusations accompanying her rejection.
There are no more uses of "petulant" in the book.
Show samples from other sources
She stomped her foot like a petulant child.
She is petulant by nature and was clearly insulted by the question.