In an interview with E!, Channing Tatum says that when he was working with Rooney Mara on The Bitter Pill that he was terrified of her. "She's the most mousy and terrifying person I've ever met." I could see that. If you watched Girl With The Dragon Tattoo and then had to work with her right after, I would be scared too.
I think it is too bad that the Swedish version came out first because then Rooney would have had more notice paid to her transformation. Noomi Rapace was great too, but Rooney's performance kind of got lost in the shuffle and when you see her now it is like that movie really did change her. When you look at her now it is like she has taken that character and kind of melded her into her own life. I don't know if it is because she has had to keep some of the body transformations for the sequel or what, but she has definitely changed.