Overgrowth (A modern First Contact story perfect for our times) - Mira Grant

At age three, Anastasia Miller walked into the forest and disappeared. Three days and six hours later, something that looked just like her walked back out. Returning home, Stasia insisted that she was an alien disguised as a human being and that the armada that left her on Earth is coming for her. Since that day, she has told anyone who would listen. No one has believed her. Until now. With an alien signal from the stars being broadcast around the world, humanity is finally starting to realize that it's already been warned, and it may be too late. The invasion is coming, Stasia's biological family is on the way to bring her home, and very few family reunions are willing to cross the gulf of space for just one misplaced child. What happens when you know what's coming, and just refuse to listen?