There is a passage on (my) page 43 that describes a bit about each of these three characters. Montag asks Millie if she knows anything about what happened to Clarisse. Millie responds nonchalantly, as if she doesn't really care at all. Montag clearly shows that he cares and this marks a significant difference between him and his wife. Clarisse is gone, terminated by the State because she was a free thinker. Millie responds, flippantly:
No. The same girl. McClellan. McClellan. Run over by a car. Four days ago. I'm not sure. But I think she's dead. The family moved out anyway. I don't know. But I think she's dead.
It is difficult to find a single passage that describes all three characters. Finding one passage for each individual is much easier. In the beginning of the novel, Montag meets Clarisse. We recognize what a free spirit she is and how she starts to spark a change in Montag: from a thoughtless drone to a thoughtful man. On page 10, Montag's description of Clarisse says a lot about her and how he is beginning to change:
How like a mirror, too, her face. Impossible; for how many people did you know that refracted your own light to you?
How rarely did other people's faces take of you and throw back to you your own expression, your own innermost trembling thought?
Montag finally meets someone who talks to (not at) him, someone who challenges him to consider things from a different perspective.
After a fire, Montag returns to tell Mildred that they burned a woman. Millie just ignores this, saying, "It's a good thing the rug's washable." She would rather ignore such things and stay within the comfort of talking about the parlour shows: virtual television shows on the walls of their home. Millie, scared of anything or anyone that might upset their way of life, says of the woman:
She's nothing to me; she shouldn't have had books. It was her responsibility, she should've thought of that. I hate her.