I've been trying to remember the name of this book, as it was the first a series. I wanted to wait until a few more books came out, but I forgot the name and my Kindle Unlimited history has been deleted. So: published between 2012-2015, available on Amazon as an ebook.
Female MC with a male friend/love interest in a post-apocalypse world. At a coming of age ceremony she is selected or passes a test that qualifies her to 'go elsewhere' and no one in the community is really sure what that is.
Turns out it is a spaceship above earth--aliens have arrived and taken over the world at some point and she is expected to adapt to life on the ship.
A big plot twist is the realization that Earth has suffered from massive radiation exposure, so much so that all humans are significantly disfigured but the alien race had brainwashed/altered the humans somehow so they don't realize it. The female MC makes the realization, hides it from the head alien in charge (who desires her as a love interest, though she's not interested?) and begins to make a plan. The novel ends with her gazing out from the ship at Earth, truly seeing the devastation wrecked on the planet and pretending to see it as the ideal Earth she has been taught to expect.
I'd really like to re-read it/read the next book, but it seems like there's been a proliferation of these sorts of stories. Anyone have a few guesses?