In 1879, following the death of her husband, Lady Wilde left Dublin for London, where she was a central figure of the circle of Irish writers, including George Bernard Shaw and William Butler Years. She contributed her poems and articles to periodicals, including The Woman's World, of which Oscar Wilde was the editor in 1887-9. Under his editorship, he raised its status (formerly called The Lady's World) from a fashion magazine for society ladies to a culture magazine for new, independent women.

During the Wilde trials in 1895, while many of Wilde's friends persuaded him to leave the country, it was Lady Wilde who insisted that he should stay and stand trial: 'If you stay, even if you go to prison, you will always be my son. It will make no difference to my affection. But if you go, I will never speak to you again.' After Wilde's conviction, however, her health declined rapidly in her despair and sorrow for 'dear Oscar'. She died in February 1896. Learning that she would not be able to see him again on her deathbed, she said, 'may the prison help him'.