Dogs of War - The Extinction Series, #5

Hope is worth fighting for. A year after the Collapse, C. O. R. E., with Bishop at its help, is finally ready to move forward with the evacuation of their elite and the resetting of Earth's clock. On the eve of war, Melanie Edwards prepares to save as many refugees as possible. With a fleet of miners and engineers turned soldier and two busted spaceships, she draws the line. She thinks she's ready to accept the consequences...until a voice drifts out of the dark and the nuclear missiles start flying.
Only halfway to Wyoming, Eve Edwards and her new family struggle to survive Earth's last great extinction event.