Oh, Kaitlyn. We've all had friends that we were BFFs with at one point, but as time passed, we grew to have absolutely nothing in common with them. That's kind of the situation between Hazel and Kaitlyn: at one point they had very similar lives, but their situations are now so drastically different that they've become different people. Kaitlyn represents what Hazel could have been if she continued blissfully on the path of most healthy teenagers—filled with school gossip and shopping and talk of boys. But that's not Hazel's reality anymore.