Final answer:
Mary, Queen of Scots ruled as queen of France and Scotland and was eventually executed by Elizabeth I for plotting against her life and throne.
Step-by-step explanation:
The historical figure described in the question is Mary, Queen of Scots. She ruled as queen of France and Scotland and was a devout Catholic. She was also the cousin and heir to the English throne. Elizabeth I kept her in captivity for 19 years and eventually had her executed for treason.