In the beginning of the movie, I was of the opinion that the point of view is really stupid. As it turns out though, the film is based on a book written by the real-life protagonist girl who was diagnosed with a terminal illness. (Tear-jerker warning.) And the film was put together by Shonali Bose, who herself lost a teenage daughter.
Overall, the result is life affirming, realisticly comedic and heart-warming. If there is a life lesson here, it is that no two people process grief in the same way.