They create and add suspense throughout the story, making the rising action mysterious and different so that once you hit the climax, what you thought was going to happen is completely different than what did
I believe that the most fitting answer for this question would be the word "giggle." Even if you have never read this story before, you can assume from the girls' laughter that what is about to happen is going to be amusing and fun. This word is the best hint that something amusing is going to happen. I hope this helps.