To those saying that Fincher noticed her from Elm Street or something to that affect, there are interviews out there where she says she has had to audition for every role. Even TGWTDT, where she said she had to audition several times over a month or two. Keep in mind that's even after having worked with Fincher (briefly) on The Social Network.
Plenty of name directors audition actors they have worked with before, and in this case Mara only had a minor role in TSN. So unless she caused such a huge impression on Fincher that he's like "I need Mara for the role of Lisbeth," I'm not surprised he auditioned for several months to find the right person.
I'm glad the context of her words was clarified. I also want to add that a lot of fans don't know how the world of actors is. I've worked for a few years in TV/film productions and I have friends who are aspiring actors, that attitude of disliking roles and big opportunities is common even for a bunch of no-name actors. I have a friend who's in a national Wal-Mart ad, his biggest break, but even he was thinking "man, this can work against me."
Think about it: You're trying to really stand out, but your so-called "big breaks" are in roles and movies that you know are going to be shitty and likely to disappear into obscurity (i.e. Elm Street remake).
I thought she was an excellent Lisbeth Salander. I think she's proven she can carry a movie playing a fairly complex character.