An older lesbian woman (I think a nurse on vacation) who encounters a girl at a beach who is playing in the sand. The girls name was Amy and she was there with her father who was always busy with work. The older woman notices that Amy gets sand in her bikini and the part I remember is how the author describes how she observes Amy's bikini bottoms pulling away and exposing a labia with sand on it as she's sitting playing in the sand.
Anyone know that story (I think it was called Sand in her Bikini) or other stories that make descriptions like that?