Anna of Brandenburg
Anna of Brandenburg (27 August 1487 – 3 May 1514) was a German noblewoman.
Margravine Anna was the daughter of John Cicero, Elector of Brandenburg and Margaret of Thuringia.
She was born in Berlin, Brandenburg, and died in Kiel, Holstein.
Princess Friederike Luise of Prussia
Princess Friederike Luise of Prussia( 29 August 1714 – 4 February 1784) was a daughter of Frederick William I of Prussia and Sophia Dorothea of Hanover and Margravine of Brandenburg- Ansbach.
Louisa Montagu Douglas Scott, Duchess of Buccleuch
Louisa Jane Montagu Douglas Scott, Duchess of Buccleuch and Queensberry( 26 August 1836 – 16 March 1912) was the daughter of James Hamilton, 1st Duke of Abercorn.
In 1884, she became the Duchess of Buccleuch and Duchess of Queensberry, the wife of William Henry Walter Montagu Douglas Scott, 6th Duke of Buccleuch& 8th Duke of Queensberry.
She was the paternal grandmother of Princess Alice, Duchess of Gloucester and of Marian Louisa, Lady Elmhirst, as well as the maternal great- grandmother of Prince William of Gloucester, Prince Richard, Duke of Gloucester and great- great- grandmother of Sarah, Duchess of York.
Hubba bint Hulail
Hubba bint Hulail was the grandmother of Hashim ibn' Abd Manaf, thus the great- great- great- grandmother of the Islamic" Nabī"( Prophet) Muhammad ibn Abdullah.
Anne Denman
Anne Denman( 1587–1661) was born in Olde Hall, Retford, Nottinghamshire.
Through a fortunate second marriage with Thomas Aylesbury, she became the grandmother of Lady Anne Hyde, Duchess of York and great- grandmother of Queen Mary II and Queen Anne.
Dorothea of Denmark, Duchess of Prussia
Dorothea of Denmark (1 August 1504 – 11 April 1547), was a Duchess of Prussia by marriage to Duke Albert, Duke of Prussia.
She was the daughter of King Frederick I of Denmark and Anna of Brandenburg.
Hannah Arnold
Hannah Arnold, also known as Hannah Waterman King, was the grandmother of Benedict Arnolds children.
Dorothea of Brunswick-Lüneburg
Dorothea of Brunswick-Lüneburg (1 January 1570 – 15 August 1649) was a daughter of Duke William "the younger" of Brunswick-Lüneburg and his wife, Dorothea of Denmark, Duchess of Brunswick-Lüneburg.
She married Count Palatine Charles I of Zweibrücken-Birkenfeld.
They had four children:
Princess Sophia Dorothea of Prussia
Princess Sophia Dorothea of Prussia  (25 January 1719 – 13 November 1765) was the ninth child and fifth daughter of Frederick William I of Prussia and Sophia Dorothea of Hanover.
By marriage, she was a Margravine of Brandenburg-Schwedt.
Maria of Mecklenburg-Schwerin
Marie of Mecklenburg, born sometime between 1363 and 1367, but probably by 1365, dead after 13 May 1402, was a duchess of Pomerania.
She was the daughter of Duke Henry III, Duke of Mecklenburg( death 1383) and the Danish princess Ingeborg of Denmark, Duchess of Mecklenburg( death 1370), was Duchess of Pomerania.

Question: Who is Dorothea Of Denmark, Duchess Of Prussia's maternal grandmother?
Answer: Margaret of Thuringia