By the suppression of truth she was slandering her.

Of course, Winnie was independent, and need not care for the opinion of people that she would never see and who would never see her; whereas poor Stevie had nothing in the world he could call his own except his mother's heroism and unscrupulousness.
The first sense of security following on Winnie's marriage wore off in time (for nothing lasts), and Mrs Verloc's mother, in the seclusion of the back bedroom, had recalled the teaching of that experience which the world impresses upon a widowed woman.

But she had recalled it without vain bitterness; her store of resignation amounted almost to dignity.
She reflected stoically that everything decays, wears out, in this world; that the way of kindness should be made easy to the well disposed; that her daughter Winnie was a most devoted sister, and a very self-confident wife indeed.

As regards Winnie's sisterly devotion, her stoicism flinched.

She excepted that sentiment from the rule of decay affecting all things human and some things divine.