Continuity mistake: When Mr. Collins introduces himself to Mr. Darcy, Mary is behind them, talking to her parents. However, you can hear Mary singing at the piano (in the next room) at the same time, and then go on to see her there in the next scene. (00:40:20)
Continuity mistake: Just before Mr Bingley proposes to Jane, when Mrs Bennet orders 'Everybody to the kitchen', Jane is holding her right hand over her left hand. When Mrs Bennet kisses her hands the next second, her left hand is over her right hand. (01:40:05)
Revealing mistake: On many occasions throughout the film, Keira Knightley's real, short hair can be seen under her wig.
Other mistake: Once Lizzie leaves the castle of Mr. Darcy, skid marks from crew trucks can be identified on the country lane leading away from the castle, where she admired the statues Mr. Darcy had accumulated.
Continuity mistake: During dinner at Lady Catherine de Bourgh's home, all five candles on the candelabra repeatedly grow taller or become shorter, depending on the angle of the shot.
Continuity mistake: Everyone is having dinner at Lady Catherine's house. Watch the candles in front of her. In the close-up shot of her face, every candle is standing up straight. In another shot, further away, the second candle from our left (Lady Catherine's right) leans towards the left side of the screen.
Factual error: The Douglas firs or Redwoods shown at the front of Longbourn (Groombridge Place) were not introduced to the UK before 1827, but the film is set in 1797.
Continuity mistake: Kitty has just spotted Mr. Bingley returning to Longbourn from the window. She is seen through the glass wearing two bangles, spaced several inches apart, on her left lower arm. Cut to the immediate next shot from inside the room and the two bangles are now on top of each other on her wrist. (01:43:50)
Revealing mistake: Throughout the dance scene between Darcy and Elizabeth, a small earpiece can be seen in Elizabeth's ear. I would assume this is to help with the dance steps. This can also be seen during the dance with Mr. Collins, however it is not as noticeable. (00:39:00)
Continuity mistake: The brown ribbon on Mrs. Bennet's bonnet during her conversation about the return of Mr. Bingley keeps moving back and forth over her left shoulder throughout the scene. (01:38:10)
Other mistake: When Darcy proposes to Lizzie notice the clock on the mantle does not change time. Nor does the clock change time when the Bennetts are discussing having the militia leave town.
Answer: According to the book, at the beginning, Jane 22, Elizabeth 20, Mary between Elizabeth and Kitty so 18 or 19, Kitty 17, Lydia 15.
Myridon