[2] The Cui clan was an eminent Chinese family of high government officials and Confucian scholars.
According to this source, Lady Cui was dressed as the wife of the heir, which was seen as an affront as the succession discussion had ended in favor of Cao Pi, so she had to die to prevent any further opposition.
The law Lady Cui violated was one of many designed to combat growing political corruption, as many people were dressing above their position to gain privileges.
[1] At the same time, Lady Cui's death was a form of suppression of Cao Zhi, relatively weakening his power and support.
Yi Zhongtian a contemporary historian said ''Cui Yan used his death to prove he was a gentleman.