Final answer:
Maria Theresa was the queen of Austria during the Seven Years' War when Prussia attacked Austria and its allies.
Step-by-step explanation:
The queen of Austria when Prussia attacked was Maria Theresa. During the Seven Years' War, which began in 1756, Frederick the Great of Prussia invaded Saxony, leading Austria, along with France, Spain, and Russia, to form an alliance against Prussian expansion. The war was part of a larger struggle for power in Europe, aimed at maintaining the balance of power, a foreign policy principle that sought to prevent any single nation from dominating the continent. Maria Theresa was the ruling Archduchess of Austria and queen of Hungary and Bohemia during this time. Her opposition to Prussia's aggression was a significant part of her reign, as she sought to safeguard her domains and maintain Habsburg influence in the region.