Question: Mary Osborne, Duchess of Leeds, born Lady Mary Godolphin, was a daughter of Henrietta Godolphin, "née" Churchill, 2nd Duchess of Marlborough, and Francis Godolphin, 2nd Earl of Godolphin, making her granddaughter to the powerful government trio during the reign of which person that became Queen of England, Scotland and Ireland on 8 March 1702?
Context: Mary Osborne, Duchess of Leeds (1723 – 3 August 1764), born Lady Mary Godolphin, was a daughter of Henrietta Godolphin, "née" Churchill, 2nd Duchess of Marlborough, and Francis Godolphin, 2nd Earl of Godolphin, making her granddaughter to the powerful government trio during the reign of Queen Anne of Great Britain: the famous general and politician John Churchill, 1st Duke of Marlborough, and his wife Sarah, Duchess of Marlborough, through her mother; and Sidney Godolphin, 1st Earl of Godolphin, through her father. The Godolphin Arabian (c. 1724 –1753), also known as the Godolphin Barb, was an Arabian horse and was one of three stallions that founded the modern Thoroughbred race horse bloodstock (the others were the Darley Arabian and the Byerley Turk).  He was named for his best-known owner, Francis Godolphin, 2nd Earl of Godolphin. John Churchill, Marquess of Blandford (13 February 1686 20 February 1703) (sometimes called Charles Churchill) was a British nobleman.  He was the heir apparent to the Dukedom of Marlborough as the only surviving son of John Churchill, 1st Duke of Marlborough, an accomplished general, and Sarah Churchill, Duchess of Marlborough, a close friend of Queen Anne.  Blandford died childless in 1703, and upon his father's death in 1722, the dukedom passed to his eldest sister, Lady Henrietta Godolphin (née Churchill). Anne (6 February 1665 – 1 August 1714) became Queen of England, Scotland and Ireland on 8 March 1702.  On 1 May 1707, under the Acts of Union, two of her realms, the kingdoms of England and Scotland, united as a single sovereign state known as Great Britain.  She continued to reign as Queen of Great Britain and Ireland until her death. Henrietta Godolphin, 2nd Duchess of Marlborough (19 July 1681 – 24 October 1733) was the daughter of John Churchill, 1st Duke of Marlborough, general of the army, and Sarah Jennings, Duchess of Marlborough, close friend and business manager of Queen Anne. Robert Spencer, 4th Earl of Sunderland (24 October 1701 – 15 September 1729) was a British peer from the Spencer family, the son of the Whig politician, Charles Spencer, 3rd Earl of Sunderland.  His mother was Lady Anne Churchill, the daughter of John Churchill, 1st Duke of Marlborough and Sarah Churchill, Duchess of Marlborough.  Known as Lord Spencer between 1702 and 1722, he succeeded to the Earldom after his father's death in, but died in 1729 with no children.  Therefore, his brother, Charles, became 5th Earl of Sunderland, and subsequently 3rd Duke of Marlborough after the death of his aunt, Henrietta Godolphin ("née" Churchill), 2nd Duchess of Marlborough. Francis Godolphin, 2nd Baron Godolphin (2 November 1706 – 25 May 1785) was a British peer and politician. Francis Godolphin, 2nd Earl of Godolphin, {'1': ", '2': ", '3': ", '4': "} (3 September 167817 January 1766) was a British nobleman and politician, styled Viscount Rialton between 1706 and 1712. Sir Francis Godolphin {'1': ", '2': ", '3': ", '4': "} (25 December 1605 – 22 March 1667), of Godolphin in Cornwall, was an English nobleman, landowner, politician, and Member of Parliament.  His chief claim to fame is that he was the dedicatee of Hobbes' "Leviathan". Marquess Grey was a title in the Peerage of Great Britain.  It was created on 19 May 1740 for Henry Grey, 1st Duke of Kent, with remainder to the male issue of his body and in default thereof to his granddaughter the Honourable Jemima Campbell and the heirs male of her body.  The Duke of Kent died only two weeks after the creation of the marquessate when the dukedom and most of its subsidiary titles became extinct (see Duke of Kent).  He was succeeded in the barony of Lucas (which could be passed on through female lines) and in the marquessate of Grey according to the special remainder by his granddaughter Jemima, the second Marchioness Grey.  She was the daughter of John Campbell, Lord Glenorchy, later 3rd Earl of Breadalbane and Holland, and Lady Amabel Grey (died 1726), eldest daughter of the Duke of Kent.  On 22 May 1740, three days after the marquessate was created, she married the Honourable Philip Yorke, later 2nd Earl of Hardwicke.  They had two daughters, Lady Amabel Yorke and Lady Mary Yorke.  Lady Grey died in January 1797, aged 73.  As she had no sons the marquessate died with her.  However, she was succeeded in the barony of Lucas by her eldest daughter, Lady Amabel, who in 1816 was created Countess de Grey in her own right (see Earl de Grey for further history of this title).
Answer: Queen Anne of Great Britain