Lots of people buy hatchery Ameraucana, not realizing that they are actually Easter Eggers. Then they breed their hatchery sourced birds and sell the chicks,insisting that their stock are pure Ameraucana, because that's what they think the hatchery sold them. They don't actually bother to check...
That's not Brown Red. Brown Reds have the same coloring as a Black Copper Marans. Hens are black with some brown, red, or gold in the neck and chest; nowhere else. The lack of muffs and beard are enough to show that she isn't Ameraucana, though.
Since the bird in question is not one of the accepted colors for Ameraucana, is not muffed or bearded, it can not be an Ameraucana. It's an Easter Egger. They are not the same thing.