Why does Daenerys Targaryen want to rule Westeros?

According to the exiled Targaryen, she is steadfast in her belief that she is the rightful heir to the Iron Throne as she is the only living descendent of the last Targaryen monarch, her father, King Aerys II. Her father was murdered by his Kingsguard, Jaime Lannister, and his throne usurped by Robert Baratheon. Daenerys believes it is her birthright to reclaim the throne.