Actually, the quote is "Lydia my love though you are the youngest, I dare say Mr. Bingley will dance with you at the next ball". Mrs. Bennet says this because Lydia is her favorite child, her mother believes she is good-tempered and bold.
Mrs. Bennet says this because she hopes that Mr. Bingley's dance with Lydia will help in securing a potential relationship between them, as well as raise Lydia's social standing. Mrs. Bennet is eager to see her daughters married into wealthy families and believes this interaction with Mr. Bingley can further that goal.
Lydia was the youngest daughter.
In Pride and Prejudice, Bingley is taken with Jane Bennet, the eldest of the Bennet sisters.
Charles Bingley
The Bennet girls are (from oldest to youngest): Jane, Elizabeth, Mary, Kitty (I believe the real name is Catherine), and Lydia. Mr. Darcy and Mr. Bingley.
Mr. Bingley dances with Jane Bennet twice during the ball in chapter 3 of "Pride and Prejudice".
There are two occasions on which Mr. Bennet refuses to go see Bingley in Pride and Prejudice. The first is at the beginning of the book, when Bingley is moving into Netherfield. The second is at the end, when Bingley returns to Netherfield. Mr. Bennet's real reasons for refusing are not really stated, as he only makes unrealistic excuses for his actions, but it is clear he does so because he likes to tease his wife.
In Chapter 2 of Pride and Prejudice, Mr. Bennet is shown engaging in witty banter with his wife, Mrs. Bennet, regarding their new neighbor Mr. Bingley. He displays his sarcastic and humorous nature, particularly in his interactions with Mrs. Bennet regarding the potential for Mr. Bingley to marry one of their daughters.
She is dining at Netherfield, the home of Mr. Bingley.
He Returns To NetherField And Proposes To Jane Bennet , Soon, They Get Married
Mr Darcy, Elizabeth Bennet, Jane Bennet, Mary Bennet, Kitty Bennet, Lydia Bennet, Mrs. Bennet, Mr. Bennet, Mr. Bingley, Bingley Sisters, Charlotte Lucas, Mr. Collins, Mr. Wickham, The Gardiners, Lady Catherine De Bourgh, Miss De Bourgh, Etc.
At the end of "Pride and Prejudice," Elizabeth Bennet marries Mr. Darcy, Jane Bennet marries Mr. Bingley, Lydia Bennet marries Mr. Wickham, and Charlotte Lucas marries Mr. Collins.
Charles Bingley's sisters in Pride and Prejudice are named Caroline Bingley and Louisa Hurst. Caroline is portrayed as being haughty and conniving, while Louisa is depicted as more reserved and passive.
When Mr. Bingley returns to Netherfield in "Pride and Prejudice," he resumes his courtship with Jane Bennet and eventually proposes marriage to her. His return brings joy to the Bennet family, especially Jane and Elizabeth.