Harry Potter readers were saying Hermione all sorts of ways before the fourth book Harry Potter and the Goblet of Fire was released and J.K. Rowling included a passage about the correct pronunciation.
It looks like J.K. Rowling has a bit of Hermione in her, as the author just confirmed that she added it in to avoid any more confusion for readers.
Harry Potter character Hermione Granger is infamous for correcting a pronunciation or two, such as her most iconic moment where she schooled Ron Weasley on the levitation spell — it’s LeviOsa, not LeviosAR!
While Hermione’s tendency to correct others produced a big ol’ sigh and eye roll from Ron, when the Harry Potter books originally came out, readers could have benefitted from a little of Hermione’s expertise, as many of the character’s names were being pronounced wrong, including her own.