Complex sentence: They lived in the London area until February 1900, when her husband became mentally ill. They retired to Bronmôr, Traethsaith in Cardiganshire until his death in 1906; she remained there until her death.
Split into simpler sentences: They lived in the London area until February 1900, when her husband became mentally ill. They retired to Bronmôr, Traethsaith in Cardiganshire. Following his death in 1906, she remained there until her death.