When Sloane opens the box of chocolates in the mall, the amount and arrangement of the chocolates changes from shot to shot.
Starting at 31:44, the candy boxes keep switching laps between camera cuts.
At 1:19:45 in, Aunt Susan's hair covers the cross on her necklace; cut to Sloane, then back to Susan, and the cross is clearly visible.
When in the tequila bar, Sloane takes off her hat and the elastic flicks her right earring off to the floor. In the next shot it's back in her ear.
At 2:00, Sloane holds her vodka in her left hand. The scene cuts to a different camera showing her drinking her vodka from her right hand.
During the Cinco de Mayo scene, Sloan loses her earring while taking off her party hat. It reappears attached during the next shot.
At 1:22, when Sloane and Jackson are grocery shopping after the turkey is burned, they're in a Sprouts grocery store. There are no Sprouts in Chicago, where the film is set, but there is one in Atlanta, where the movie filmed.