Other mistake: Barbara and Violet are talking in the car after returning from the funeral and all of the windows are closed, even though great effort was made to convey the fact that temperatures were in excess of 100°. They spend three to four minutes talking in the car and neither even breaks a sweat, when in reality, they could not have sat in a closed car in that kind of midday heat for more than 30 seconds or so without becoming incredibly uncomfortable.
Factual error: Near the beginning of the movie, the Slowhand album is on the turntable and the song "Lay Down Sally" is playing. The needle is near the end of the record, even though the song is the third of five tracks. Near the end of the movie, Meryl Streep drops the needle much closer to the beginning of the record to play the same song again.