I know you Catholics are TAUGHT this; but it sure would be a bit easier to swallow if something; just ANYTHING had been written about Mary after John took her in; other than this stretch of the Word by Rome.
I think what is lost in all of this is that by the time John penned the book of Revelation that Mary had long been expired. The chapter of Rev. 12 was more about the future of the Church as signified by a woman than any person. This is consistent with the symbolism of a pure woman being a church with pure doctrine and a harlot being a church with polluted doctrine.