I would recommend that you read chapter 9, in the book Understanding Ellen White, edited by Merlin D. Burt. The response given bellow is lifted from the book on How Ellen White Did Her Writing, by Denis Kaiser.
"Ellen White acknowledged her own grammatical and literary deficiencies, as a result, she employed a number of literary assistants (as did Jeremiah, Paul, and Peter). The task performed by these assistance may be divided into four categories: recording oral material in shorthand (stenography); simple copying by hand or typewriter (copying); correcting spelling and grammar as well as eliminating unnecessary repetitions and improving sentence structure (copyediting); and compiling materials for the writing of books (major editorial compilations). However, not every assistant was involved to the same extent in the production of Ellen White's writings. Thus her literary assistants may be divided into two groups: copyist and trusted compilers. Copyists performed the task belonging to the first three categories, whereas trusted compilers were also allowed to perform the fourth task, namely taking sentences, paragraphs, or a section on the same topic and idea from one manuscript and integrating it into another manuscript. The introduction of new thoughts of their own or changing ideas was strictly prohibited, which illustrates Ellen White's understanding of inspiration working on the thoughts and ideas rather than the exact words."