The 1890s saw a renewed focus on her literary career. She joined the newly formed Society of Authors and established a School of Literary Art. She had taken a business-like approach to her writing, retaining the copyright of her novels and syndicating her shorter fiction to regional publications. Like her contemporaries Charlotte Riddell and Mary Elizabeth Braddon, she discovered that editing a magazine was a good way of getting her own work before a wider audience. She edited London Society between 1872 and 1874, and contributed to a number of other periodicals.
Whilst working for a London newspaper in 1874, Florence interviewed a prominent clairvoyant, and that marked the beginning of a lifelong belief in spiritualism. She became a keen participant in seances, claiming to have communicated with her brother Frank, who had died in a shipwreck, and her two dead daughters. Her experiences were chronicled in in the hugely successful There is No Death and its sequel The Spirit World. Her interest also informed her fiction writing in such novels as The Strange Transfiguration of Hannah Stubbs and The Clairvoyance of Bessie Williams.
Her spiritualism provided much comfort as her health began to fail. Newspapers started reporting her decline in the summer of 1899, and she passed away on 27th October of that year at her home in Abercorn Place, London. The death certificate shows that she died of diabetes and pneumonia, and she was accompanied by Herbert McPherson. McPherson also attended the funeral and was left money in her will. After a short service in a Catholic church, she was buried at Kensal Green Cemetery, alongside her beloved daughter Eva, who had died of blood poisoning at the age of 32. Among the mourners were friends and family, and colleagues from the worlds of literature and the stage. Her epitaph read: “Past, to where beyond those voices there is peace.”