She knew well--as who would not ?--what Mona Crozier was hoping to see, and she was human enough to feel a kind of satisfaction in the wife's chagrin and disappointment; for the unopened letter in the baize-covered desk which she had read was sufficient warrant for a punishment and penalty due the little lady, and not the less because it was so long delayed.

Had not Shiel Crozier had his draught of bitter herbs to drink over the past five years?
Moreover, Kitty was sure beyond any doubt at all that Shiel Crozier's wife, when she wrote the letter, did not love her husband, or at least did not love him in the right or true way.

She loved him only so far as her then selfish nature permitted her to do; only in so far as the pride of money which she had, and her husband had not, did not prevent; only in so far as the nature of a tyrant could love--though the tyranny was pink and white and sweetly perfumed and had the lure of youth.

In her primitive way Kitty had intuitively apprehended the main truth, and that was enough to justify her in contributing to Mona Crozier's punishment.
Kitty's perceptions were true.

At the start, Mona was in nature proportionate to her size; and when she married she had not loved Crozier as he had loved her.