Mrs. Dickinson is the widow of an RAF pilot who died five years ago, and who is marked by the way that emotionally her life shut down with her husband's death. We are told that she only cried once after his death and refused to shed any tears in front of her son, Frederick, who now, unaccountably, has fits of crying. She is a character who insists on proper decorum in her life and to whom appearance is everything. She has massive expectations of both herself and Frederick, and as the story makes clear, these expectations are too much for Frederick's young shoulders.
She is extremely troubled by his tears and cannot understand why he should cry so much. Note how she responds to his crying fit:
She whipped out a handkerchief and dabbed at him with it under his grey felt hat, exclaiming meanwhile in tearful mortification, "You really haven’t got to be such a baby!"
She is a character who, having repressed her feelings with the death of her husband, is now so detached that her life is one big act. Tears are viewed by her as a sign of improper feminine weakness that she has done everything she can to shun. Mrs. Dickinson is therefore viewed as a product of the stiff-upper lip society of British culture, which has unfortunately distanced herself both from her son and also her own emotions, and she is shown to be worser off as a result.