possible additions to heighten the embarassment NAME_1 will feel when she realizes she was naked the whole time:
NAME_1 jogging over to NAME_2 and NAME_3 which would make her bare breasts bounce dramatically for them to see.
NAME_1 turns and bends down to pick up a shell, giving NAME_2 and NAME_3 a view right into her vagina.
NAME_1 trips on a sandal, stumbles, and accidentally bounces her bare breast against her niece's face.
please add more to the list