Just as Vashti was punished for crimes related to her refusal to expose herself in front of a raucous crowd of her husband's guests so are women in her Airyanem land now suffering for their appearance if they are not wearing what the law considers appropriate covering or undesireable additions such as face or unnatural colourings. What lengths are human beings prepared to go to in order to control others according to their own insecurities? Is a woman wearing nail polish really such a threat? Maybe if it is poisoned and she accidentally scratches someone in order to free herself from the constraints of the fashion police, but then that sort of resistance might lead to the death penalty.
Vashti wasn't a threat.She was battling to defend her nation from internal attack. You will have to read the book to discover what happened after she refused to be dictated to about her appearance.