Mildred, in Fahrenheit 451, is trapped in conformity. She is a product of her society.
She is a product of mindless entertainment and a system designed to keep people from thinking for themselves. She watches TV on three walls and can't stop thinking about the day when she'll get a fourth wall. The programming is so simplistic and unenlightening that a ten-year-old child would get bored with it, but Mildred watches it faithfully. She conforms to society by being engrossed with its mindless programming.
Mildred also conforms concerning the issue of books. She is the one who informs on her husband because he is too nonconforming--he reads books. Importantly, she gives little effort to understanding any of the words in the books Montag tries to interest her in. This, too, is conformity.
Her conformity is also apparent in the horror she feels when Montag reads a poem (nonconformity) to her friends. She is threatened by anything that her society doesn't sanction.
Perhaps the only nonconformist act on Mildred's part, in fact, is her attempted suicide. This, apparently--since the technicians are so nonchalant about pumping out her stomach--is what conformity in her society often leads to.
The way in which Mildred is depicted reflects a great deal about Bradbury's take on conformity in social orders. Mildred is very content living in the socially dictated conditions that are laid out for her. She is almost phobic of any expectation that goes against such an order. When Guy does not question his consciousness, their marriage is fine. When he does, friction results. Mildred demonstrates conformity with such a narrow conception of marriage, where consensus based results supersede all else. At the same time, her obsession with television, a medium that is controlled by external forces, reflects how conformist views of the social order have impacted her. Yet, in the end, Mildred cannot stop the feeling that what has been presented for her in terms of social expectations and conformist norms might be lacking an element of pure totality. Her friction with Guy, the difficulties endured as a result help to bring to light that something is "wrong" and that change has permeated a setting where it had been repelled. The underlying element that shows how conformity might be a limited concept would be that Mildred lacks the vocabulary to articulate that something is wrong with her world. Being a product of absolute conformist values, she does not know how to speak of a condition where discontent is present. Her taking of the sleeping pills is the only response that she can muster. It is one that tells Guy that something is indeed wrong with the social conditions in which he lives and used to substantiate, a sentiment confirmed with the nonchalant response of the medical staff tending to Mildred.