which country did she rule?
Scotland.
Mary, Queen of Scots
Mary, Queen of Scots (8 December 1542 – 8 February 1587), also known as Mary Stuart or Mary I of Scotland, reigned over Scotland from 14 December 1542 to 24 July 1567.

how old was the queen of scots when she died 44 years old ( 1542-1587). who is this queen? The Queen of Scots.
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Mary, Queen of Scots [SEP] Introduction
Four years later, she married her half-cousin, Henry Stuart, Lord Darnley, and in June 1566 they had a son, James. In February 1567, Darnley's residence was destroyed by an explosion, and he was found murdered in the garden. James Hepburn, 4th Earl of Bothwell, was generally believed to have orchestrated Darnley's death, but he was acquitted of the charge in April 1567, and the following month he married Mary. Following an uprising against the couple, Mary was imprisoned in Loch Leven Castle. On 24 July 1567, she was forced to abdicate in favour of her one-year-old son. After an unsuccessful attempt to regain the throne, she fled southward seeking the protection of her first cousin once removed, Queen Elizabeth I of England.