Why does Miss Strangeworth feel that she is justified in sending the letters?

In Shirley Jackson’s “Possibility of Evil,” Miss Strangeworth feels justified in sending the letters to the townspeople because she believes that it is her work to keep the town “clean and sweet.” She views the town as “her town” and the people as “her people,” so it is her duty to know everyone else’s problems, whether real or imagined. It is also her duty to warn people of possible problems that may come their way. She believes that “people everywhere were lustful and evil and degraded, and needed to be watched; the world was so large, and there was only one Strangeworth left in it.” She sees herself as the town’s caretaker who ensures that everything runs smoothly in the town. Notice that she detests “sloppiness of any sort,” and she is quick to notice that Miss Chandler, for instance, has not made her hair on a given day and that most of the town people “seem disturbed” in recent days. She sees it as her role to maintain order in the town and the letters are a means of achieving this goal.
Further, she dismisses the pain that the anonymous letters may cause the recipients by claiming that “wickedness is never easily banished, and a clean heart is often a scoured heart.” She believes that the letters are so helpful to the recipients that the pain they cause is little payment for the overall good received.