Complex sentence: Her first appearance at Covent Garden in London was in 1967, Adelaide in Richard Strauss's "Arabella", and returned in 1975 for Andromache in Michael Tippett's "King Priam".
Split into simpler sentences: Her first appearance at Covent Garden in London was in 1967 Adelaide in "Arabella" of Richard Strauss. She also performed there Andromache in Michael Tippett's "King Priam".