Among the lessons that might be taken from "The Open Window" one important one has to do with the repression of women in a patriarchal society. Vera is not merely a mischievous girl but a cruel girl. Being a female, she is confined to the house and cannot go shooting with the three macho males. No doubt she would like more freedom and adventure, as her story about the feral dogs in India suggests. Her story about the three men being sucked into a bog may be a sort of wish-fulfillment. In other words, she might have thought about this misadventure long before Framton Nuttel ever appeared on the scene. Vera might be compared with Ibsen's Hedda Gabler, a woman who becomes cruel because of being forced into a passive domestic role for which she is temperamentally unsuited. Vera takes her anger and frustration out on poor, neurotic Framton Nuttel, another male.
In Ibsen's Hedda Gabler, Tessman's Aunt Juliana represents the stereotypical domestic female of the period and serves as a foil to Hedda.
She is the quintessential nurse, willing to sacrifice herself for others. Only in that does she find much meaning in life. In this respect, and in most others, she is a stark contrast to Hedda, who detests her.
Likewise, Vera's Aunt Sappleton represents domestic women of Edwardian England and serves as a foil to Vera, who probably detests her too and sees her future in this brainless woman who is so exclusively devoted to her three men that she can only talk about the one subject that interests them: killing birds.
Vera is described as calm, cool, poised, and self-possessed, but underneath that young and innocent facade there is a very different person brooding, one who is preoccupied with cold and morbid fancies and developing a sadistic, passive-aggressive character.