"There is only one who is nude in this salon," the prince said.

Nude means that she only did not wear underpants.
But you must be informed that the salon was in Spain of about 1400.
No Eastern woman wore underparts, even if she was princess.　 　How about Western common women?
So, she should not be ashamed of herself. 　"I am the standard of the culture of that white Japan."
Maybe, the prince tried her.