In ep. 1.05 Mary-Ellen Walton makes butter in bibs and barefeet, while reading and putting her bare feets on the table. Her mother Olivia puts her feet down. On the left is John-Boy in his light blue bibs with suspenders. I like historical farm work. But again I don't know if this is realistic (fashion and behavior) especially for this religious family of the 1930s. I think Mary-Ellen is about 15ys. The milking is the job of John-Boy. Also an outside butter scene in ep. 01.19 also reading but with shoes. In ep. 14 she lies on her bed in bibs. Aren't bibs dirty after farm work and playing?
Image at bottom shows Mary-Ellen in dress, then John-Boy in his light blue bibs, Jason (rarely without bibs in the earlier seasons) and Ben in his too small bibs (ep. 1.09). I think they were at school. In an earlier episode Mary-Ellen wants to spend her money for a baseball glove, but she bought a dress to attract her boy friend while another girl likes a dress, which is for sale at Ike Godsey's (see image in post Waltons Season 1). Mary-Ellen and her mom didn't like the dress, so she returned it.