At this point, issues of class and gender are inextricable entangled. By the process of stepping out of her class to defend the workers, and also protect Thornton, she has stepped out of her gender as conventionally constructed. She has "turned herself into a public woman, an actress not an anger, potentially a fallen woman."
In order to make her an "honest woman", Thornton must marry her; that is his duty. "This public perception is internalised by Margaret herself as a sense of sexual guilt. In respect of womanly 'purity', as with her social class, she is a divided self."