Answer:
Step-by-step explanation:
The best answer is infatuated. It seems like she is really falling for him. And they and up laughing just to laugh which sort of hides a nervousness. If they were older, the best answer would be appreciative, because their laughter would have to have a trigger of some kind. So a joke an awkwardness itself (like falling when skating -- something would have to cause the laughter).
But they're young and they are delighted with each other and laughter is their outlet.