The picture enlarged but, still not good enough. Her legs/feet aren't the correct color for a Barred Rock female (usually black wash over yellow legs) barring doesn't look right.
Maybe a mix, or poor quality hatchery bird.
I’m pretty sure it’s a Maran then. The black and white ratio + patterns are more similar to a Marans than a Barred Rock, but I’m not 100% on that. A hen’s first egg is always exciting!