This is Elizabeth’s cry of pure, unadulterated joy after she has accepted Mr. Darcy’s proposal and all secrets are revealed. The use of hyperbole—”happiest creature in the world”—perfectly captures the overwhelming and triumphant nature of her feelings. It is the emotional climax of her journey. Having navigated misunderstanding, prejudice, and social obstacles, her happiness feels earned and absolute. The author brilliantly contrasts Elizabeth’s expressive joy (“I laugh”) with her sister Jane’s more serene disposition (“she only smiles”), reinforcing Elizabeth’s vibrant and spirited personality which the reader has come to love. This quote resonates with the profound satisfaction of a love that has been hard-won, representing the ultimate triumph of the novel’s central romantic theme.