Novel 2: Does Lady Dedlock Have to Die?

As I read about Bucket and Esther's frantic attempts to discover Lady Dedlock's whereabouts, I felt relatively relaxed and unconcerned because I knew they would find her alive. I was so sure that Dickens would create a happy ending involving Lady Dedlock and use her and Sir Leicester to make a statement on the merits of forgiveness for past sins. I also thought that he would create a happy ending with her and Esther by having Lady Dedlock fulfill the motherly role that Esther longed for her whole life. After all, Esther not having a mother and the mystery surrounding her birth play a large role in the book. Therefore, when they found Lady Dedlock dead, I was obviously shocked. I am very curious why Dickens "killed her off," so to speak. Perhaps Dickens could not imagine a happy ending involving Lady Dedlock that would be plausible in Victorian society. After all, in most novels written during the Victorian period that involved (to them) sexually immoral women, the unwed mother or unfaithful wife are always punished in a sense, whether by death or shunning by society. Maybe he was afraid that readers simply would not accept an ending where Lady Dedlock ends up happy because they were accustomed to characters like her being drastically punished for their actions.
I think that it is perfectly plausible for Lady Dedlock to have lived and Esther still be happy with Mr. Woodcourt. Though the prophesy about the sins of the mother passed on to the daughter sort of foreshadows a tragedy, it would have been the ultimate redemption had Lady Dedlock returned alive. She had a whole crowd of forgiving people waiting for her, and Dickens could have used the opportunity to show the merits of forgiveness. I also suppose I am kind of biased because I was quite fond of Lady Dedlock.
In conclusion, I simply had Dickens wrong. In the future, I will hesitate before trying to predict plot twists and endings.