Winstead has always been a likable presence in light fare like “Scott Pilgrim vs. the World” and “Live Free or Die Hard,” but few could have been prepared for her funny, sad, raw performance as an alcoholic who struggles to get sober in “Smashed.” Hollywood loves when a pretty girl gets down and dirty, but this is no stunt. The film is much better than it sounds on paper, with a surprising sense of humor, and Winstead is fantastic without ever being showy.