In the movie when Mia's grandfather says 'It will be okay if you leave' Mia decides to let go. Then why she stays in the end, is it because of the news of her admission in Juilliard? Or she does not have the choice at all to stay or leave? Because in the beginning nurse tells her that its only she (Mia) controls everything and if she want to live she better start fighting. I am confused now.

Towards the end of If I Stay Mia's grandfather says 'It will be okay if you leave'. Mia then decides to let go and die.

However, given this, why does she stay in the end? Is it because of the news of her admission to Juilliard? Or does she not have the choice to stay or leave (because in the beginning the nurse tells her that its only she (Mia) who controls everything and if she want to live she better start fighting)?