She can certainly clarify who she means. But if she is following SDA doctrine, it is not unclear who she means.
They associate Rome with Babylon, and the churches that hold to doctrines which she taught to be her daughters.
They saw Luther, etc. as good in their time. But after the churches rejected the first angel's message through Miller, they see a decline in these churches. So while most see Adventists as restorationist, they see themselves as continuing the reformation.
There may still be children of God in the churches, who have not yet heard the SDA message for this time, but they are to come out.
Read this whole chapter:
m.egwwritings.org
In Revelation 17, Babylon is represented as a woman, a figure which is used in the Scriptures as the symbol of a church. A virtuous woman represents a pure church, a vile woman an apostate church. Babylon is said to be a harlot; and the prophet beheld her drunken with the blood of saints and martyrs. The Babylon thus described represents Rome, that apostate church which has so cruelly persecuted the followers of Christ. But Babylon the harlot is the mother of daughters who follow her example of corruption. Thus are represented those churches that cling to the doctrines and traditions of Rome and follow her worldly practices, and whose fall is announced in the second angel's message.