Final answer:
Lady Catherine does not mind Elizabeth's simple dress because it confirms the social hierarchy, where Lady Catherine’s own superior status remains unthreatened by Elizabeth's modest appearance, which underscores the societal expectations of the time.
Step-by-step explanation:
In chapter 29 of Pride and Prejudice, Lady Catherine de Bourgh does not mind Elizabeth Bennet being simply dressed because it does not threaten her own status and also because Elizabeth's appearance supports Lady Catherine's preconceived notions about the social inferiority of the Bennets.
Lady Catherine, being from the upper class, is expected to be more elaborately dressed than those beneath her social standing, such as the Bennets. By seeing Elizabeth in simple attire, Lady Catherine's expectations are met, and thus her own sense of superiority is maintained.
Moreover, Jane Austen uses this scenario to highlight social norms and the rigidity of class structures during the Regency era.
Elizabeth's simple dress epitomizes the socio-economic distance between her and Lady Catherine, reinforcing the social hierarchy of the time. This disparity is used by Austen to subtly critique the limitations placed upon women in society, where appearance and marriage prospects are heavily scrutinized.
Given that Elizabeth does not come from wealth, her simple dress aligns well with the societal expectations and conventions that define her family's status.