Complex sentence: She made her stage debut at the Théâtre-Italien in 1883, as Amalia in "Simon Boccanegra", as a last minute replacement for Fidès Devriès, and shorthly after made her official debut as Elvira in "Ernani".
Split into simpler sentences: She made her stage debut at the Théâtre-Italien in 1883, as Amalia in "Simon Boccanegra", as a last-minute replacement for Fidès Devriès. Shortly afterwards, she made her official debut as Elvira in "Ernani".