In London, Elstob translated Madeleine de Scudéry's Essay upon Glory in 1708, and an English-Saxon Homily on the Nativity of St Gregory in 1709 Both works are dedicated to Queen Anne, who is praised in feminist prefaces.
From 1702 Elstob was part of the circle of female intellectuals around Mary Astell, who helped to find subscribers for her Rudiments of Grammar for the English-Saxon Tongue (1715), the first such work written in English.
The preface, "An Apology for the Study of Northern Antiquities", took issue with the formidable Jonathan Swift, and seems to have caused him to amend his views.
She tried to start a girls' school in Chelsea, but despite obtaining so many pupils that she had "scarcely time to eat", they only paid a groat (4d.)
In 1718 she fled London and her creditors, leaving behind her books and a partial manuscript of Ælfric’s Catholic Homilies which she had translated.
She lived there for many years dependent on her friends, running a small dame school under the assumed name of Frances Smith.
In the autumn of 1738 Elstob was introduced to the wealthy Margaret Bentinck, Duchess of Portland, and was made governess to her children, remaining in her service until her death, at Bulstrode Park, Buckinghamshire, on 3 June 1756.