I think that Dahl's story gives us insight into Mary's psyche. It is one rooted in fixed conceptions of the good. When these are interrupted, panic sets in and horrible actions ensue. Mary's desire to retain fixed conceptions of the good or aspects of traditional reality are seen in how she covers up her crime with a trip to the grocer's and fixing dinner for the officers who will "search for her husband's killers." As she listens in from the kitchen, insight is given into how Mary reveres traditional construction of reality so much that she will do anything to preserve it.
I think that it might be a stretch to suggest that this is a view into the psyche of women, in general. Certainly, the initial feelings of anger and betrayal that Mary feels can be something that most people, men and women, would process at the moment they are blindsided with the news that their relationship is over. However, I think that the consider Mary's actions of murder and coverup as reflective of the psyche of all women or women, in general, is not accurate. It reduces women to a caricature and denies the full spectrum of experiencing actively nuanced emotional responses to being in the world.