Complex sentence: She cast herself as Myrtle and her real-life daughter, Donna Damerel, as Marge, with Myrt the elder, experienced chorus girl taking young, inexperienced, and innocent Marge under her wing.
Split into simpler sentences: She cast herself as Myrtle and her real-life daughter, Donna Damerel, as Marge. Myrt was the elder, experienced chorus girl taking the young, inexperienced, and innocent Marge under her wing.