Yeah, I got the metaphor. And she can still be a candle maker as her day job, as her cover, while she is abusing her powers.
What does "light the way" mean translated into a plot? Her objective goal is to rescue her brother. It seems to me she has to discover how to "light the way" for herself -- subjective need -- before she can do it for anyone else. If her brother is trapped in physical darkness, she's trapped in spiritual darkness.
Or framing if from another perspective: if she's already got the "right stuff", she just needs to use it, then what's her character flaw? What is there for the audience to worry about? That she is doomed because her powers are no match, never will be, for the sorcerer? Not likely if the story has a happy ending.
So, again, what is there for an audience to worry about? What if she has an "Achilles heel" (character flaw) which, when all else fails the sorcerer -- her powers prove equal to his -- threatens to be the means for him to prevail against her? And not just prevail but destroy her?
I see the story in the mythical mold of the Hero's journey, a call to adventure (linked to an objective goal) which implicitly entails a challenge to change, to grow (linked to a subjective need).
fwiw.