Yeah OK whatever.
I sense irritation in the force...
Let me put it another way. Blight you can hurt, push out of the way, even shape by sheer willpower. It's one of the reason she doesn't get bonuses against your diplomacy checks despite the fact that she's got a decently high will, you WANT her to go along with what you're saying and therefore she is more likely to go along with it.
You=Blight, Blight=You. Thus anything that can affect you can and must effect blight in equal measure,
because you are both products of the same mind. Your will is effective when it is focused on something that can be changed by sheer willpower, like your own mind. Even more so when aided by empathetics.
Sample 18 is a very real fungus which is in your very real head. Willing at it is not going to make any difference, because, let's face it, it is a fungus. It has no conception of willpower, all it knows is food and its own crude system of hijacking neurons.
So in short, the only thing your brain has the power to change on will alone are things that are part of itself. The fungus, not being a part of you, cannot be directly affected by a simple act of will.
Now, I'd hoped you (or someone helpful) would think of this sooner, but I'm going to give you a hint.
How was your fungus controlled in the first place, at the very beginning of your introduction? To be entirely honest I've written the turns for everyone but Taric and you, and I'm mostly done with Taric's, but I'm going to give you a bit more time. Just in case inspiration were to strike.
(That and I feel like hell. I'm not entirely altruistic here.)