She was the only daughter of Spencer Cowper, lawyer, judge (Justice of the Common Pleas), and member of Parliament,[2] and his wife Pennington (née Goodere; died 1727),[2] and is thought to have been born at the family seat, Hertingfordbury Park, Hertfordshire, England.

[3] Her original characterisation of Abelard prefigures the Romantic era hero: Laura Alexander, the academic and fellow of the American Society for Eighteenth-Century Studies, says of Cowper's creation that, "in her Abelard [is] an original pathos figure that anticipates the "man of feeling" in later eighteenth-century literature of sensibility.

[1][3] On 7 December 1723 Cowper married Colonel Martin Madan,[1] groom of the bedchamber to Frederick, Prince of Wales, and MP for Wootton Basset.

[5][6] Their younger daughter, Penelope (died 22 December 1805), became the wife of General Sir Alexander Maitland (1728–1820).

Judith was the aunt of William Cowper the English poet and hymnodist, and grandmother of General Frederick Maitland.