If her legs aren't yellow she is not a barred rock. Not all Marans have feathered legs, either.
Now an eye opener for newbie chicken owners...... Anyone who owns chickens, hatches eggs and sell chicks, can call them selves "Breeders". I have been breeding chickens for 40+ years and would never classify myself as a Breeder.
IMHO a "Breeder" has learned everything that they can possibly learn about the breed they are breeding. They have obtained the very best breeding stock they can afford, and they are very conscientious about culling to choose only the best examples of the breed to breed forward.
There is the chance she is a crossbred mutt, because a lot of people are not able to tell the difference between different breeds of "barred" breeds.
If she is a mutt, you are not the first person that bought a chicken that was not what the chicken was presented to be. And sometimes the person was not intentionally misrepresenting the chicken, they simply did not know any better.
She will probably be a great layer, what ever she is!
lolDon't even get me started on dogs and horses.
I love to call people up and ask them the sire and dam of the horse they have for sale for $2,000. Some of them don't even know what a sire or dam is.......
And dogs...... Are their eyes checked? They look good to me! How about OFA on hips? Is OFA a disease? But, they want $1,500 for this dog!
Back to discussing chickens !