That's sort of the problem though.
Alleria in novels, in the history, is fairly well rounded. She has motivation, she has clear goals, her character is conflicted, but it's rooted at a ground level to events in her life.
The introduction of the void here has somewhat trivialized that history. Now it's about her tackling with the void and others fearing whether she would succumb. While it's nice to see progression in her character beyond simply being a faithful servant of the light alongside Turalyon, I feel like this whole void issue was tacked on and could have been applied to practically any character to 'give them depth'. And we've had this sort of thing happen so many times now, especially in BFA, that it's just not interesting to explore any more IMO. We have plenty of curses and power-shifts that I think it actually takes away from her character more than adds to it. I think if they just kept it grounded and had her have a motivation to reject the light (like say she saw X'era's acts as going too far) it might have served her better purpose in the story. Right now she's being played out as a ticking timebomb.
So did Garrosh by absorbing the full powers of the heart of Y'sharjj, and they literally treated it like nothing. Willpower has a lot to do with it and Alleria is one of the most hardened characters in WoW. I could see them giving us a plotline with her that makes it seem like she's going mad but her being in actual control, just to play up the drama with Turalyon and co. I don't see them going full blown making her Sylvanas 2.0. It'd be redundant.Could she fall to the whispers? It's likely, she's got more grape juice in her than any other