Wow, big contrast. I would had thought the back of her leg slate/black from the first photo. Many barred rock hens tend to have splashes of dark on their legs, even going all the way down to the foot. I don't know that I've ever seen as an extreme version as this hen but it could be that. I bought a local flock once from a guy who had easter eggers and one turned out to be a cockerel that looked pretty much like a barred rock (with flaws in regards to SOP obviously). I'd still wager some sort of mixed breed or that his stock is basic hatchery stock, which realistically is the same thing as a mix breed (to a degree).
If he hatches his own chicks, and you know him - I'd make an inquiry of what breeds he has in his flock (if it's that important to you); if not, then I'd still call her a barred rock; as mentioned, there isn't much difference in regards to most hatchery stock birds and that's what people commonly expect..
I found the farm on the internet and she noted that she "raises purebred hens and a few roosters that I hatch here and/or arrive at a day old." I am sure I could contact her and find out more information.
I will call her a Barred Rock. She may have a different variation of leg coloring but I am fine with that.
Hopefully all Barred Rock Chicken lovers accept her as she is.