If you think that there is a god (an assumption), what do you expect him to do to prove that he is such a god?
I can easily think of a hundred ways how a god could offer such a strong evidence to its existence that people dismissing it would be reduced to conspiracy theorists. If a sun stops being a sphere and reforms itself into fiery letters stating the god's existence, of course people could still say that NASA faked it or that it's a practical joke of some inconceivably advanced alien race, but then they'll be the ones wearing the tinfoil hat.
But this is not the kind of evidence I would expect from the woman. She does not claim to be a god, she claims to be a true prophet. I expect her to demonstrate it with accurate prophecies. If she announces the location, day, hour and minute of several major earthquakes in the next year and gets them all right, that is an example of almost perfect evidence for her claim, as accusations of deception would be implausible. Guessing the contents of a box is not nearly so perfect - but hey, it's still good! If she does that, the door will be wide open for her to bring even better evidence. If she fails, she remains a woman saying stuff.
Different people will require different levels of evidence; some will believe anything you tell them, some will never believe you no matter how much evidence you bring. I have met people who refused to believe simple, provable mathematical truths on grounds of their philosophical reasoning. Does that make the proofs invalid? Of course not. - So does it really matter whether you convince this or that particular skeptic? Some people already believe the woman (you being an example). If she wins the Million Dollar Challenge, millions more will believe, and if she keeps doing stuff like that, believers will keep pouring in. I think that's what should matter to you when it comes to the importance of winning the challenge.