Good point, not a pullet at age 2. I mis-typed.She's 2yrs old, not a pullet.
I'm certain it's the mother's side. But will find out when I do the breeding experiment next spring. It is a theory.
If it is actually an allele of the barring gene, she did NOT inherit it from her mother. Barring is on the Z sex chromosome, which a hen gets from her father but not her mother. Her mother gave her a W chromosome (that's why she's female.)
So if she did inherit this trait from her mother, it is not on the Z chromsome, and it cannot be any allele of Barring.
Or, taking it the other way around: if it is an allele of the barring gene, she inherited it from her father, not her mother.