I would really recommend reading the book yourself first before making any decisions. Of course, whilst the rating applied to the movie can be a useful guideline, we all know that movies are not necessarily accurate to the original spirit of the book, and often add scenes that might be more mature in order to gain a wider audience. Thus the best advice I can give you is to read it yourself. You know your daughter better than anyone else and her own level of maturity and what she can and can't cope with.
I'm not sure about the book, but the movie was rated PG-13. It's good to seek advice when you don't have the answers, but the best course of action would be to read the book yourself. Only you can really judge if it's a book that YOUR 8 year old is mature enough to read. Good luck.