Shelia Naylor's insecurity stems from her family's recent socioeconomic ascent; her father's newfound wealth leaves her feeling alienated among St. Clare's established upper-class students. This insecurity manifests as behaviors her classmates interpret as pretentious "airs and graces," breeding their widespread dislike. A pivotal incident occurs when Sheila uses the phrase "didn't ought to" in conversation, provoking Janet to publicly rebuke her grammar: "Haven't you learnt by now that decent people don't say 'Didn't ought to'!...you talk like the daughter of the dustman!" This humiliation intensifies Sheila's social struggles, with the narrative directly linking her acute sensitivity to criticism to anxieties about her family's "new money" status and unacknowledged social standing.

Later, Sheila gains a neutral-to-positive peer interaction by being assigned prompter for the first form's Christmas play. Head girl Winifred James contextualizes Sheila's behavior for the twins, clarifying that her perceived snobbishness is a defensive reaction to feeling excluded from St. Clare's traditionally genteel environment.