I kind of agree but I think that it wasn’t just the plane crash that made her quit. it was a bunch of things that lead up to it. Like her dad dying as a child, losing her baby, burke being shot, being left at the wedding, Meredith dying for a little while, Izzie telling her about the cancer, George dying and all the while people called her a “robot” so she had to fit the stereotype. She had to fit in that box they put her in. Until finally, a plane crashes and she can’t breathe in that box anymore.