If the author helped with it and was overseeing it (as celtrose said) then she must be ok with it and it would have to follow her style and skill for that. Just think of it as a REALLY good fanfic.
I've only started watching the HP films. And I used to read then book when I turned 14 but got bored after GoF. But in starting to read them all in Spanish
YAS
YAS
YAAAAASSSSSSSS