Actually, I don't think it matters even if she could show malice. Truth is an absolute defense against an accusation of libel, so long as the facts exposed were obtained legally.
That's the other side of her two-pronged burden of proof as I understand it: (a) that the claims are false and (b) that the authors acted with malice.
But you're right, if the authors can prove truth, it's over. My point is that the authors can win by knocking down either prong.
I welcome correction to my understanding of this.