Question: Whom was the sister of a prominent figure in the Restoration court and an influential friend of Queen Anne of Great Britain?

Context paragraphs:
Queen Anne (play): Queen Anne is a 2015 play by the British playwright Helen Edmundson on the life of Anne, Queen of Great Britain.  It is set between just before her accession in 1702 and her husband George's death in 1708 and centres on the relationship between Anne and her close friend Sarah, Duchess of Marlborough, by whom Anne was heavily influenced in the period before and during her reign.

Queen Anne's Bounty Act 1714: The Queen Anne’s Bounty Act 1714 (c 19) is an Act of the Parliament of Great Britain.  It is one of the Queen Anne's Bounty Acts 1706 to 1870.

Queen Anne style architecture: The Queen Anne style in Britain refers to either the English Baroque architectural style approximately of the reign of Queen Anne (reigned 1702–1714), or a revived form that was popular in the last quarter of the 19th century and the early decades of the 20th century (when it is also known as Queen Anne revival).  In British architecture the term is mostly used of domestic buildings up to the size of a manor house, and usually designed elegantly but simply by local builders or architects, rather than the grand palaces of noble magnates.  Contrary to the American usage of the term, it is characterised by strongly bilateral symmetry with a Italianate or Palladian-derived pediment on the front formal elevation.

Queen Anne's Bounty Act 1707: The Queen Anne's Bounty Act 1707 (6 Ann c 54) was an Act of the Parliament of Great Britain.  It was one of the Queen Anne's Bounty Acts 1706 to 1870.

Queen Anne's County, Maryland: Queen Anne's County is a county located in the U.S. state of Maryland.  As of the 2010 census, the population was 47,798.  Its county seat and most populous municipality is Centreville.  The census-designated place of Stevensville is the county's most populous place.  The county is named for Queen Anne of Great Britain who reigned when the county was established in 1706.

Frances Talbot, Countess of Tyrconnel: Frances Talbot, Countess of Tyrconnel ("née" Jennings, previously Hamilton;  1647 – 9 March 1730) was a prominent figure in the Restoration court, together with her younger sister, Sarah Jennings.  Once a maid of honour to the Duchess of York, she was twice widowed and eventually died in poverty.

Kingdom of Great Britain: The Kingdom of Great Britain, usually called Great Britain or Britain was inaugurated in 1707 with the union with Scotland.  It did not include Ireland, which remained a separate realm.  The Stuart rule ended in 1714 with the death of Queen Anne.  Her close relatives were all Catholic, and were prohibited from the crown, so the Hanoverian succession brought to the throne George I, the ruler of the German state of Hanover.  George I continued to rule Hanover and annoyed many Britons by putting British weight behind the needs of that small country and entangling Britain in its diplomatic conflicts.  The years 1715-45 saw attempted Jacobite risings against the Hanoverian kings; the revolts had some support in Scotland and some aid from France, but they were all quickly suppressed.

Sarah Churchill, Duchess of Marlborough: Sarah Churchill, Duchess of Marlborough (née Jenyns, spelt Jennings in most modern references; 5 June 1660 (Old Style) – 18 October 1744) rose to be one of the most influential women of her time through her close friendship with Queen Anne of Great Britain.  Sarah's friendship and influence with Princess Anne was widely known, and leading public figures often turned their attentions to her in the hope that she would influence Anne to comply with requests.  As a result, by the time Anne became queen, Sarah’s knowledge of government, and intimacy with the Queen, had made her a powerful friend and a dangerous enemy.

Judge Jefferson Thomas Cowling House: The Judge Jefferson Thomas Cowling House is a historic house at 611 Willow Street in Ashdown, Arkansas.  It is a 2-1/2 story wood frame structure exhibiting architectural styling transitional between the Queen Anne and Colonial Revival styles.  It features the asymmetrical massing and busy roof line of the Queen Anne style, with a projecting corner section with a conical turret, while its porch columns are more classical in form than those typically found in the Queen Anne.  The house was built in 1910 for J. T. Cowling, one of Ashdown's most prominent early settlers.

List of English monarchs: This list of kings and queens of the Kingdom of England begins with Alfred the Great, King of Wessex, one of the petty kingdoms to rule a portion of modern England.  While Alfred was not the first king to lay claim to rule all of the English, his rule represents the first unbroken line of Kings to rule the whole of England, the House of Wessex.  The last monarch of a distinct kingdom of England was Queen Anne, who became Queen of Great Britain when England merged with Scotland to form a union in 1707.  For monarchs after Queen Anne, see List of British monarchs.

Supporting paragraphs: Frances Talbot, Countess of Tyrconnel Sarah Churchill, Duchess of Marlborough
Answer: Sarah Churchill, Duchess of Marlborough