A "radical" is someone who fights strongly against the status quo. When confronted with the word, Lyddie immediately thinks of the Quakers, whom she has found to be "abolitionists, every one". At the boarding house at which she Lyddie is staying, Diana Goss is considered to be a radical. She is a member of the "Female Labor Reform Association", which is a union, and her "crime has been to speak out for better working conditions" for the women who work in the factories. Lyddie's roommates warn her about associating with Diana Goss. Union activity is strongly condemned by the companies that employ the girls, and the boarding house residents are afraid of the repercussions Lyddie may have to face if she should become involved with Diana and her politics.
Diana has shown nothing but kindness to Lyddie, however, taking her under her wing and showing her the intricacies of operating the dangerous looms at the factory. Lyddie "had no desire to anger her roommates, but she was quite set on going to see Diana...she wanted to learn everything - to become as quietly competent as the tall girl". Diana gives Lyddie the materials to write to her family when she first arrives in Lowell, and finds a doctor for her when she is sick. The more Lyddie associates with Diana, the more she is overwhelmed by the sheer goodness of her heart.
Diana does educate Lyddie about the burgeoning labor movement, and she invites but never pressures her to participate. Lyddie discovers that despite her "radical" bent, Diana's motivation is the welfare of the girls, whom she looks upon as "sisters". Diana is a "radical" because she truly believes that unionization will better their lives (Chapter 9).