Mary was the seventh child and fourth daughter of George II and Caroline of Ansbach. After her mother's death in 1737, Mary was brought up by her elder sister, Princess Caroline. In 1740, she was described as 'a lover of reading and far more solicitous to improve the mind than to adorn the body'. Horace Walpole, who had played with her when they were both children, said she had 'the softest, mildest temper in the world'. When she was 17, a marriage was arranged for her with Prince Friedrich of Hesse-Cassel (1720–85) and they had four children. Her married life was very unhappy, however, and in 1746, she returned to Britain for a time, to recover from her mistreatment. Prince Friedrich converted to the Roman Catholic faith and this gave Mary the excuse to separate from him in February 1755. Mary did not return to England but stayed with her children, supported by her father-in-law, Wilhelm VIII, who provided a residence for her at Hanau. She died at Hanau on 14 January 1772.

The artist, Christian Frederick Zincke (1683/4-1767), was born in Dresden, the son of a goldsmith. He settled in England in 1706 and studied enamel painting under Charles Boit. Boit was Enamel Painter to the Court until Queen Anne died in 1714 when he moved to France and Zincke took over much of his work. Zincke developed a thriving business, at first copying portraits by Sir Peter Lely and Sir Godfrey Kneller, then painting from life. He worked extensively for the royal family and, perhaps because he spoke German, was one of the few artists George II could tolerate. By 1730 he was well established at court and in February 1732, was appointed Cabinet Painter to Frederick, Prince of Wales, George II's eldest son. His eyesight began to fail, however, and he lamented: 'I find my Eyes scarce Capable of seeing them fine strokes'. By 1752 he had retired and only painted for his own pleasure. George II commented that Zincke's portraits were 'beautiful and like'.

The miniature was probably painted from life by Zincke shortly after the series of her sisters dating from 1729-30.