A righteous and reasonable question asked deserves a considered and thoughtful answer. So, I responded to her query. I explained that there had been much study and scholarly discussion as well as more than a bit of ranting over the geographical features of Middle-earth. I went on to say that vast amounts of verbiage have been devoted to determining an accurate depiction of this or that bend in the river or the road. Treatises have been penned regarding the exact location of landmarks mentioned only in passing in Tolkien's writings.
Carried along by my own fervor, I also explained that the typography of Middle-earth under-went cataclysmic upheaval at the end of the Second Age. I did not, however, press the matter further by attempting an explanation of how the Valar 'bent the earth' and removed the Blessed Realm to a place beyond the physical approach of Men. That would have been asking for too much forbearance from someone who had little interest in the subject. I did tell her that the debates over the geography of Middle-earth was only the 'tip of the iceberg'.
My friend ruefully responded that she should never ask questions about things like changes to mythical geography unless prepared to endure the answer. She was reminded of a cartoon in 'The New Yorker': St Peter sits at his podium before the Golden Gate between two portals - one marked 'Loved the Three Stooges' and the other marked 'Hated the Three Stooges'. She related this to Tolkien fans and non-fans saying, "The Tolkien thing is definitely a binary decision: one gets it or one doesn't get it."