The Light chooses its own champions - those who it deems fit to use it. How or why it chooses, it does not answer. But if a Guardian is meant to be a stalwart and moral person, it may have been attracted to you because you are one.

[That Rose is still being flippant might mean that she's unaware of the gravity of this choice. Or perhaps she is flippant because she does. Either way, it's not a solemn thing! Her face lights up, quite literally so as the Mark of A'dal ignites above her forehead. She reaches out as if to hug her, and settles for resting her hands on the human's shoulders.]

This is a cause for celebration, Rose! There is no greater honor or blessing than to be chosen by the Light.