The Bad Miss Bennet by Jean Burnett
Ever wonder what happened to poor Lydia after she and Wickham were sent away at the end of Pride and Prejudice? I guess Jean Burnett did, too. Although this story smacks of far different stories than Jane Austen's, it's a valid possibility. Burnett's work tackles what became of Lydia after Pride and Prejudice, and I can kind of see how she could become this woman.
Wickham died, technically, in battle. It's not true, but the way things went down, it could be believed. Lydia is not much for widowhood. She's still very young, a lot more worldly and looking for her second chance in life. She finds a way to get money out of her wealthy brother-in-law and sets off to see what life has to offer.
In her time with Wickham she learned how to scam people. She's good with cards and everyone knows that she was born to flirt. She and her friends host parties and try to make enough money to keep them afloat, usually to pay off their debts and throw more parties. Of course, they run afoul of the law and Lydia is once again turning up at Pemberley seeking shelter and money.
Lydia's taste in men has not improved and she takes up with a handsome highwayman. This leads her into a new life of intrigue and murder and romance. It's not Austen, but I really did feel like it was Lydia. I admit this is a strange statement. Burnett did not write in Austen's style at all, but she definitely did hold true to the personalities of Austen's famous characters.
If you are looking to check back in with the Bennet girls, you could probably do a lot worse.