Continuity mistake: When Sheba is standing outside of the car talking to Barbara in the scene where she has to choose between her son's play and consoling Barbara, the passenger door is shown opened, then closed, then opened etc.
Continuity mistake: There's a scene where Barbara Covett is writing in her journal and the voice-over refers to it as "A Gold Star Day," and we see a close-up shot of Barbara's index finger pasting a gold star on the page of her journal; her fingernail is unpolished and just a bit grimy. In the next shot, we see Barbara still writing in her journal but now her nails are polished pink. (You can see this in the clip "Gold Star Day," which is on the film's website).
Continuity mistake: Sheba's eye makeup in the scene where she confronts Barbara keeps changing. One moment it's thick and black, the next it's barely visible, then it's streaked and smeared, then it's back to thick and black, etc.