[2] Her next performance was on 3 January 1811, where she played Lady Anne in Richard III with George Frederick Cooke in the title rôle.
[2] Other roles she played at this time were Miranda, with her husband as Marplot, in The Busy Bodie by Susanna Centlivre; and Eliza Ratcliff, with John Bernard as Sheva, in The Jew by Richard Cumberland.
On 29 April 1811 the Duffs appeared at a benefit in which Mary danced a solo while her husband performed in The Three and the Deuce by Prince Hoare.
Mary's first season in Boston ended with her playing Victoria in Hannah Cowley's A Bold Stroke for a Husband.
Ellen Darley (née Westwray) retired as leading "juvenile lady"; as a result, Mary stepped up and succeeded to most of her characters.
He had been for some time in poor health and had declined in professional popularity, while his wife, at first viewed as inferior to him in ability, had surpassed and eclipsed him.
After her husband's death, Mary had a hard struggle with poverty, as she was the mother of ten children and actors, even of the best order, were poorly paid in those days.
An article in The Philadelphia Sunday Mercury, 9 August 1874, written by James Rees, relates the strange circumstances of her burial.
There seems to have been a purpose to conceal the identity of Mrs. Sevier with Mrs. Duff, and to hide the fact that the mother of Mrs. Reillieux had ever been on the stage, – but the grave of the actress was finally discovered and restored.