Final answer:
Madame Defarge pinning a rose in her hair often signifies a non-verbal signal or message to her allies, particularly in the context of literature like 'A Tale of Two Cities' where it indicates an enemy's presence.
Step-by-step explanation:
The significance of Madame Defarge pinning a rose in her hair in literature often symbolizes a message or a signal to others. Although the question cites a number of different contexts where roses and adornments play a role in conveying status, wealth, and identity, such as Marie-Antoinette with the rose and Madame X's portrayal, it is important to bring our focus directly to the novel concerned to understand the significance in that particular literary context.
For example, in Charles Dickens's novel 'A Tale of Two Cities', Madame Defarge pins a rose in her hair to signal to her revolutionary comrades that an enemy of their cause is nearby. This action sets off a chain of events and communicates danger without the need for words, indicating the powerful symbol of a rose within the narrative.