There is plenty of evidence in “The Open Window” that the ironically named Vera has the habit of making up stories. Within the framework of a comparatively brief story, she makes up two, one for the benefit of each of the other principal characters. In beginning the story, what she tells Framton suggests a history of lying including, perhaps, at least one experience of being caught out in a verifiable lie. She carefully ascertains that Framton does not know Mrs. Sappleton and that his sister, who does, has not seen her for four years. Vera then conveniently places the tragedy three years ago and displays considerable histrionic talent in relating it. The song, which she presumably knows the men are likely to be singing when they return, is a particularly artistic touch. When Framton has gone, she is, of course, at liberty to invent a highly-colored story set in India to explain his curious behavior.
The final sentence of the story confirms what the reader has presumably worked out for him or herself by this time: “Romance at short notice was her speciality.” This makes it clear that Vera makes a habit of telling these stories and has honed her skills of improvisation and dramatic delivery of them to a fine art.