Final answer:
Marie Antoinette's quote is ironic because she lost her head during the French Revolution, despite the advice she gave. It highlights the contrast between her extravagant lifestyle and the consequences she faced.
Step-by-step explanation:
The quote from Marie-Antoinette, 'When everyone else is losing their heads, it is important to keep yours,' is ironic because she herself lost her head during the French Revolution. The quote suggests that one should remain calm and composed in a crisis, but Marie-Antoinette's reign was marked by her extravagant spending and disregard for the struggles of the French citizens, which ultimately led to her downfall. Her quote is now seen as a dark and ironic commentary on her own fate.