The French sister Suzanne is played by Pauline Etienne, who was born in Belgium. In The Nun's Story (1959), a similar movie based on the real life story of a Belgian nun who also wants to leave her convent, Sister Luke is played by Audrey Hepburn who was also born in Belgium.
Lead actress Pauline Etienne, who plays Suzanne Simonin, appears totally/full frontally nude after she disrobes in front of two nuns.