She was born in 1682 and married Robert Walpole, the first PM in British history who served from 1730-1742. Lady Walpole died in 1737 and was already estranged from Robert when Jervas painted this portrait. The Philip Mould notes for this include the following: “Removed from the sober aspect of his male sitters, Jervas’s women invariably inhabit a world tinged by fantasy. The myth evoked is more immediate that the Arcadian reverie of Van Dyck and Lely – his shepherdesses and milkmaids are more contemporary than Greek – but they exude the same ease and complacency. Here Lady Walpole pretends to gather flowers in her garden, just as the Duchess of Queensberry, in a contemporary portrait by Jervas (London, National Portrait Gallery), pretends to be a milkmaid. The garden through which she wanders is loosely suggested, and the mood evoked is that of an Italian villa, as in the distance a raised tazza spills water amid a grove of young trees. The flowers that Lady Walpole carries in her hand and in her basket are magnificently painted and repay close examination. Whether they are the work of Jervas or of a studio specialist is not known, but the burst of color they provide in the lower right of the canvas is a splendid counterpoint to the restrained blue and red of her costume and the muted tone of the sky and enclosing trees.
Stylistically it must date from the early 1720s, which would be compatible with the sitter’s apparent age, allowing for conventional flattery, whilst the architectural background would seem to allude to Houghton Hall, without depicting it with any accuracy. Jervas is usually more precise in such settings, and the loose suggestion of the Palladian façade dates the painting to the period before the final form of the house had been realized. The original Campbell design for the house saw a square plan with Palladian pedimented towers at the four corners of the building, but these were never executed. In 1725 this lack was resolved by the Baroque cupolas currently visible, which were erected to the design of Gibbs. Its seems likely, therefore, that the portrait of Lady Walpole was painted c.1722-1725, and the unusual ziggurats in the background reflect an uncertainty as to the intended effect.
Whether Catherine Shorter deserved this elegant treatment is less certain. She and her husband married in 1700, but soon began to seek diversion elsewhere. The birth of Horace Walpole in 1717 was a surprise to many, given the couple’s known feelings for each other, and gossip was swift to name others as the father. Lady Mary Wortley Montagu suggests that the true father was Carr Hervey, elder brother of Lord Hervey, and it is true that Walpole seems more to resemble the Herveys than his named father. Lady Mary further speaks of Lady Walpole as ‘an empty, coquettish, affected woman, anything rather than correct in her own conduct or spotless in her fame.’ When she died of dropsy in 1736 it is recorded:
‘Sir Robert it is likely is not very sorry: she was as gallant if report be true with the men as he with the women, nevertheless, they continued to live together, and take their pleasures their own way without giving offence.'"
Her Wikipedia article is here.Charles Jervas' Wikipedia article is here.