Complex sentence: Keith has regularly appeared on stage across the country, including a role in Noël Coward's "Star Quality" and in 2004, she played Madame Arcati in "Blithe Spirit" at the Savoy Theatre.
Split into simpler sentences: Keith has regularly appeared on stage across the country. This has included a role in Noël Coward's "Star Quality", while in 2004 she played Madame Arcati in Coward's "Blithe Spirit" at the Savoy Theatre.