Ivory/Albino Paradox? Chimera? What is this thing?

[asplundii]

This is close to what we believe as well, but it's obviously less likely that both parents are hidden hets rather than just one or the other.

While it may be less likely that both parents were unknown hets it is even more unlikely that you would see a case of a mosaic with regionalized alternating monoallelism happening so that you get patches that are entirely Albino/YB and patches that are entirely non-Albino/Ivory but no patches that are non-Albino/YB or Albino/Ivory

I'm not sure if there were fire siblings or not, but it shouldn't matter if there were. She was bred to both males and siblings could have been sired by either.

Superficially, yes it does not matter. But, if in all the other siblings there are no Fire or WT then the statistical odds of this one animal being from a different sire are much reduced. And if you can pin down the likely father then you can consider proving it out as het Albino at some later date.