.
So much of eroticism is in the mind.
.
Plus she was said to have had an incestuous relationship with her father, so the nudity reinforces the horror of what happened.
This is an excellent example of how nudity is not added for gratuitous purposes but because it's essential to the plot.
I'm pretty sure that some of the ladies in silhouette while they're changing clothes in Gold Diggers of 1933 are nude.