I have been hearing a different story for years. She actually did say, “Let them eat cake,” in response to the French people refusing to eat potatoes in the face of the famine. The aristocracy ate potatoes, but as potatoes are in the deadly nightshade family, they were considered poisonous like tomatoes, so poor people would only grow the grain they had grown for generations. She was not being callous, but frustrated by the people’s refusal to eat something that would grow in the changing climate.
That’s a nice story - it doesn’t make her seem like a vapid spoiled rich person - but there is no evidence to correspond to the story.