Seen the movie? (It's very good. Though Darcy isn't as icy in the movie, mostly because his actor is kind of adorable to me.)
Keep in mind that aloofness as a trait is also heavily romanticized...
I don't know that aloofness is the right word... she sort of just passes through life in a kind of haze, but rather than not comprehending or paying attention to her surroundings, she simply appears disinterested or... I dunno, irrationally surprised in an understated manner towards the things around her that she really should treat in a more mundane, lively manner.
For example, one of the other main characters is completely in love with her and has been for a long time, but she basically never acknowledges it. At one point another character asks here directly whether she knows or not, and her reaction basically amounts to "yes, I've known since the day I met him." Upon being asked what she feels about it, she essentially says "I'm not sure; I've never thought about it."
Of course, that's not really true
, but she has a sort of established bubble that she doesn't let anything get inside of and that she tries to use to push the outside world away from her...