Complex sentence: Maria Theresa, who then attempted to influence Amalia into giving up her immoral activities, was told off in no uncertain terms and Amalia remained estranged from her mother (despite her mother's repeated efforts at reconciliation) for the rest of the Empress' life.
Split into simpler sentences: Maria Theresa, who then attempted to force Amalia into giving up her immoral way of life was told off in no uncertain terms. Amalia would remain estranged from her mother despite the lstter's repeated efforts at reconciliation for the rest of the Empress' life.