Complex sentence: Her last novel was "Daniel Deronda", published in 1876, whereafter she and Lewes moved to Witley, Surrey; but by this time Lewes's health was failing and he died two years later on 30 November 1878.
Split into simpler sentences: Her last novel was "Daniel Deronda", published in 1876, after which she and Lewes moved to Witley, Surrey. By this time Lewes's health was failing, and he died two years later, on 30 November 1878.