The story of Daisy Miller is above all one of warning. The way in which Daisy Miller stubbornly refuses to heed the advice and repeated warnings she is given about her impropriety of spending time with a man such as Giovanelli without a chaperone and the insistence with which she continues to break social norms and customs clearly results in her exclusion from the society of expatriates of which she is a part. Daisy Miller is above all a character who stubbornly clings to what she thinks is right and acceptable with tragic consequences.
Therefore, I don't think we can blame "worldly evils" for her death in any way. In fact, I almost think that James allows her to die as a kind of merciful end to her story, because the logical conclusion of her life would have been to have found herself severely compromised through her relationship with Giovanelli or with another Italian lover, which, James infers, would have been a fate worse than death. Daisy Miller therefore is a character who deliberately took risks with her reputation and her name, which in turn led her to take risks with her health. Ignorance is not an excuse, as the repeated warnings amply testify. Therefore Daisy Miller's death is a result of her own stubborn-mindedness and her own reckless indifference to the well-meant advice that others give her. Note the way that the casual mention of her death in the four words, "The poor girl died," seems to cement her own insignificance and the way that her behaviour had already moved her beyond the conversation of respectful society. In a world where your standing in society meant everything, her death was probably a merciful release before other events transpired that would have completely ruined her name and reputation forever.