That doesn't look like a black; blacks can have some/many "scattered white hairs" but they're not usually arranged the way they are on your bunny. But it's not really an identifiable color/pattern yet either. It's so hard to say what's behind colors like REW and himi/cal, or even self black to some degree. They can cover up so many other genes. It's when you breed them with another color that all sorts of unexpected things can crop up.
I've found that lots of NZ whites are actually chestnut, chinchilla or steel "underneath" the white. That steel <Es> is a tricky thing (or maybe more than one thing), and so is the gene for silvering <si>. Hard to say for sure from the photos, but it looks like your bunny has white hairs rather than white-tipped hairs. So, <si> is the one I'm wondering about for your "black" rabbit.
The silvering gene is supposed to be recessive, but it's one of the least understood and might involve more than one gene, or be strongly affected by modifiers, or both. I know that in some cases it is partially dominant, meaning that it can show up in a reduced form in animals that carry only one copy of it; in others it is completely recessive, having no expression at all in an animal that is heterozyous, i.e. <Sisi>. I crossed a purebred Californian into my purebred Satin line some years ago to improve my Satins' growth rates. In the first generation I got "blacks" that had so much silvering that I actually showed them successfully as Silvers (while they were juniors). I never did the breeding experiment that would have shown for sure they carried <si> - I wanted to get rid of the white hairs in my Satins, not produce more white hairs - but I kind of wish I had.
The champagnes and silver fox I've watched grow have differed pretty dramatically from individual to individual in their development of silvering, and those are animals that are homozygous for silver <sisi>. I'd say that if you continue to see an increase white hairs as she grows, that would suggest there's a stealth silver gene in there (probably coming from the cal dam).
If it was me entering her in the fair, since she's a mixed breed, I'd enter her as a silver rather than a black. I could see her being DQ'd for excessive white hairs in a black, while in a silvered rabbit the silvering shows up, as I said, sequentially, and juniors are not expected to be fully silvered, so she may be given the benefit of the doubt. And with luck, between now and the fair she'll develop even more silvering to make the pelt more attractive (for meat and fur purposes).
Here's one of my "silver" juniors at about 10 weeks; she continued to develop more white hairs as she grew, though she never got any silvering on her head.
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