Mary Tudor, Romantic Rebel
Mary Tudor, betrothed first to a boy four years younger than her, and then to a man over 30 years older than her, married Louis XII, King of France when she was just 18, and he 52. Three months later, the King was dead, and she was a widow.
Before marrying Louis, she had extracted a promise from her brother that her second marriage would be her choice - a promise Henry agreed to, probably just to get her to France with as little fuss as possible.
Regardless, Mary would hold Henry to that promise, and when Charles Brandon, with whom she was already in love, came to bring her home to England, she took her chance and married him, risking the anger of the notoriously temperamental Henry.
You can read more about her rebellion in the name of romance here.