Maybe you and she need to pay a little more attention to the resiliency of life as a whole.

There is a future, and the point in trying to live is that the future will be a lot worse if you don't try to live it. Anxiety over an uncertain future, one that may well not be as good as one would like, is understandable--probably even healthy as otherwise one might be tempted to ignore the dangers.

But calculating the geometric series of something that doesn't work geometrically, and then plugging in numbers three times too high, is not sensible "back burner anxiety". It is fearmongering. It's probably not your daughter's own fearmongering--I expect it's encouraged by others.

Maybe the biggest problem your daughter faces isn't the future but the people assuring her that the future will be baaaaaaad. The future will be filled with challenges, but save for something truly cataclysmic like global thermonuclear war, the challenges will (mostly) be surmountable.