James uses a fair bit of alliteration in the novella, especially in the narrator's insights into Winterbourne's thinking and the dialogue between Winterbourne and Daisy. This frequent alliteration gives the narrative a musical quality and the characters an air of playful eloquence.
For example, when Winterbourne charges Daisy with being a flirt, she responds with an alliterative burst:
I’m a fearful, frightful flirt! Did you ever hear of a nice girl that was not?
This alliteration of the /f/ sound in the phrase "fearful, frightful flirt" underlines the conflicting sides of Daisy's character. As a literary device, alliteration elevates the poetic effect of a given phrase or text. At the same time, one doesn't necessarily need a great amount of depth or sophistication to use alliteration. Similarly, Daisy is beautiful, and in certain respects stylish, without being particularly sophisticated. She would rather have fun with her speech than use it to prove her intelligence or refinement. The purpose of her alliteration isn't to express profound ideas but to reinforce her own playfulness.
Daisy's acknowledgment that she's a "fearful, frightful flirt" reflects her simultaneous self-awareness and obliviousness. On the one hand, she shows that she knows how other people see her—and that she takes pleasure in acknowledging it. Downplaying the seriousness of the accusation with the words "fearful" and "frightful," she expresses that, unlike the American expatriates who disapprove of her behavior, she doesn't see it as a big deal.
On the other hand, Daisy also proves her lack of self-awareness with this alliterative remark. Only interested in her own inclinations, with no concern for place-specific rules of conduct, Daisy makes fun of anyone who disapproves of her behavior. This freedom of mind is admirable to a certain extent, but it ultimately leads to her social demise (and arguably the sickness that takes her life).
