I'm working on a post now. 
I'm wondering if my character can reduce the power of her fire balls to simply light torches rather than explode like a grenade, or if she can only light some of her body on fire rather than all of it (increasing the time she can have that body part stay lit by the amount of her body not on fire). If this is okay I'll say she can do it. It will come in handy, possibly much sooner rather than later. For example, even if they didn't have torches she could just light a finger on fire or someone to be a mini torch.