These are addresses where YOU can write a letter to Emma Watson; (she will deffinately reply from this address, i have tried and she replied, it just takes a few months ... these are all I know of so far, so its worth a try!:
Emma Watson
c/o Harry Potter Productions
Leavesden Studios
PO Box 3000
Leavesden, Herfordshire, WD2 7LT
United Kingdom
Another one is:
Emma Watson
C/O Warner Bros. Inc.
3300 Warner Blvd.
Burbank, CA
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