If you go through the book you will soon see what the themes are ..basically ...dedication,elitism,snobbery,betrayal and loyalty.
She is such a snob and only really wants to have "her girls"around her and to teach them her ideals to the exclusion of others. Her "creme de la creme ". ..elitism. She is dedicated to her profession but in a skewed way.She only wants to teach them what she thinks is right ,so selfishness could be another theme. The girls are loyal to her but betray her finally when one of them shops her for her facist views.