Other mistake: When Whoopi first takes over the choir, she asks the sisters to stand according to their singing voices. She asks where the sopranos are, and several women on opposite corners of the grouping raise their hands. She asks them to all move over to the left group, but only one of the two women on the right side actually does so.
Other mistake: During the 'Rescue Me' montage, when Maggie Smith catches Whoopi Goldberg singing whilst washing the car, Whoopi reacts to her and then there's a brief moment where she looks straight at the camera.
Other mistake: When Mary Clarence enters the choir room the first time, Mary Lazarus approaches and asks only if she's a soprano or alto, when there are lower voiced baritones and bass nuns in the group.
Answer: It is because she is not, technically, a nun yet. She is a novice, one who is in the "trial period" of becoming a nun, but who has not made the final vows to join the order.
Twotall
She doesn't wear a white cap in the second movie either, and she did her vows.
It takes 9-12 years to become a nun, with many stages: discernment, aspirancy, postulancy, novitiate, temporary vows, and finally, solemn vows. The young nun may have moved up a step but would not yet have taken her solemn vows. The various stages would have differences in apparel, headdress, insignia, etc. that showed their rank. In addition, different nun orders wear different styles of habits.
raywest ★