The status of Ellen White is the question outsiders ask first, and the church's answer is more carefully worded than either its critics or its enthusiasts usually report.
She wrote enormously, books, articles, letters, testimonies, across seventy years, and her output shaped Adventist practice on health, education, diet, dress and mission. The church holds that she possessed the prophetic gift, and that her writings are a continuing authoritative source of truth and comfort. It also holds, formally and in its published statement of beliefs, that the Bible is the standard by which her writings must be tested, and not the reverse. Adventists therefore describe her as a lesser light pointing to the greater, and reject the description of her writings as scripture.
That distinction is genuinely load-bearing in internal debate, and it is also under pressure from a documented problem. White borrowed extensively from other authors without attribution, a practice examined at length from the 1970s onward and confirmed by studies the church itself commissioned. The church's position is that borrowing was a normal nineteenth-century practice and does not bear on inspiration. Critics inside and outside hold that it undermines claims of direct revelation. Both readings are live within Adventism.
Her most visible legacy is the health message. Adventist teaching commends a vegetarian diet and abstention from alcohol, tobacco and, generally, caffeine, and treats the body as a stewardship. This produced a major medical and educational network, Loma Linda University and a global chain of hospitals and schools, and one unusual secular consequence: Adventist populations have been studied by epidemiologists for decades as a long-lived cohort, and Loma Linda is routinely cited in longevity research on the strength of it.