Genetically, something isn't right here. That mix of breeds should not be able to produce a hen with dark-colored legs like hers.
Maybe either the Wyandotte or the White Leghorn was carrying a gene that is wrong for their breed. The gene in question is on the Z sex chromosome, which a hen...
Is she a standard sized hen, or a bantam?
If bantam, I'm going to guess the father is a Buff Laced Sebright and the mother is a Black Tailed Japanese Bantam (white or buff, wouldn't matter.)
If she is standard sized, I agree with the others who think Wyandotte is in the mix. Her father is not...