Complex sentence: Horn further developed and consolidated the "Ibsen Festival" and led Nationaltheatret through the 100-year anniversary in 1999, on that occasion, she was appointed Commander of the Order of St. Olav.
Split into simpler sentences: Horn further developed and consolidated the Ibsen Festival, and led the Nationaltheatret through its 100th anniversary in 1999. On that occasion, she was appointed Commander of the Order of St. Olav.