Hubby and I talked a bit about this...he feels that if you take the book at face value and do not interject any other notion (movie portrayal of the mirror scenes for example), then no, Hermione does not know how the mirror worked until after the confrontation at the end of the school year. Then I got to thinking...Ron knew about the mirror because at Christmas time he and Harry saw it together, but when you read carefully, you see that Harry did NOT tell Ron how it works, just that he needed to stand just so to see anything.
But I think that with JKR's use of the word, 'everything', you could safely assume Harry told them how the mirror worked. Just my two cents.
|A little of this, a little of that, a lot of confusion. That's my life!|