To friends and teachers, the death of Winnie Henri reflects the pain - economic, social, and emotional - that young Haitian emigres, uprooted by natural disaster and personal hardship, often suffer in silence in the United States. And for Partners in Health, one of Boston’s highest-profile charities, her sudden death under its supervision has prompted soul-searching and questions about whether Henri, who received medical care here two years ago, later tumbled through the cracks toward a lonely and unattended death. “Everyone associated with the case is devastated,’’ said Ted Constan, chief operating officer of Partners in Health.