Winterbourne is never evil. One cannot imagine him being energetic or decisive enough for that. However, in this passage he does think rather severely of Daisy, though, typically, he allows several possible explanations for her behavior.

Having arrived in Rome, Winterbourne quickly realizes that Daisy is not popular among the American expatriates there: she is not invited to their houses, and she is generally regarded as "abnormal." The American community regards her conduct as not absolutely scandalous, but indecorous and indiscreet, and they do not wish for their Italian friends to meet her or think of her as a typical American.

In this passage, Winterbourne is wondering whether Daisy even realizes that she is being ostracized. Perhaps, he thinks, she is too frivolous, unsophisticated, and childish to have noticed. This is his first negative reflection on her character, contained in the sentence quoted. However, he also wonders whether Daisy is aware of what people think of her and is being deliberately defiant by pretending not to notice. In this case, he thinks is possible that her defiance springs from a sense of injured innocence. However, there is another, more negative, interpretation: that she is defying public opinion thorough sheer recklessness and does not care what impression she makes on anyone.

What are Winterbourne’s negative thoughts about Daisy in the following passage?

“Winterbourne, who denied the existence of such a person, was quite unable to discover; and he was divided between amazement at the rapidity of her induction and amusement at the frankness of her persiflage. She seemed to him, in all this, an extraordinary mixture of innocence and crudity.”

It would be quite wrong to call Winterbourne's thoughts here (or anywhere else) evil, and even to regard them as particularly negative seems somewhat severe. What Henry James is really showing is the difference in temperament and personality between Winterbourne and Daisy. In particular, he illustrates the degree to which Winterbourne generally misunderstands her, as well as how he seems to find her forwardness and youthful energy rather taxing. (Winterbourne is only twenty-seven himself, but the reader is apt to forget this, as he always seems so much older.)

All that has happened is that Winterbourne has just announced his intention of returning to Geneva the following day. Daisy pretends to assume that there must be some beautiful woman who has captivated Winterbourne and lured him away to Geneva, refusing to allow him a moment longer in Chillon with her (hence the reference to Winterbourne denying "the existence of such a person"). Winterbourne is entirely unused to women talking to him in this way and does not know what to make of it—whether to think that Daisy is being childishly frank or assuming a knowing air unbecoming to a woman of her class and station. Perhaps the best description of Winterbourne's thoughts about Daisy would be "bewildered" or "mildly shocked, but still intrigued"—which is to say, only slightly negative.