Without much to go on, I chose to start my research on the Lyttons with the biography of Rosina Lytton, which was written after her death by her literary executrix, Louisa Devey. (Interesting side note: Devey had previously tried to publish some of Edward Bulwer Lytton's letters to his wife, in response to a partial biography published by his son. She had been thwarted in that attempt by the son, Robert, who was able to obtain a court injunction against their publication). Devey's sources include Rosina's "manuscript autobiography" and "other original documents."
In the biography, Rosina's childhood is described in almost ridiculous detail, but her adolescence is quickly glossed over. The narrative then progresses rapidly through her courtship, marriage, and practically immediate disillusionment with her husband. He is described as being physically as well as emotionally abusive to her. After about nine years of marriage, Edward and Rosina separated, and two years later he took custody of their two children against her will. A long and nasty litany of court cases and libel actions then ensued, during the course of which Rosina was – by her account – physically kidnapped and held at a posh insane asylum in the country for about two weeks, after which time "public outrage" forced her husband to release her. She was reduced to living on a very small income, more or less alone, while her husband became a wealthy and respected author and public servant.
Stylistically, I have some misgivings about this source, because the narration is at times very dramatic - so much so that I think it must have been embellished. The autobiographical portion was obviously written later in Rosina's life, and partly with the agenda of refuting the claims made about her by her husband and his mother. She takes a lot of trouble to show that he was the one pursuing her, and claims that initially she was not at all interested in him. Devey's writing is less heavy-handed than Rosina's, but over all the thing reads like a badly-written novel, which really doesn't help its credibility.