This does look authentic to me. Jennifer Love Hewitt actually wore this one.
Anyway, if you ever want to be really sure if it's authentic, there are 2 really easy ways that most of the fake ones don't replicate.
1. the fabric. Authentic ones lay flat flat when laid down, and are not as stiff, and are stretchier.
2. the Herve Leger tag. Compare it against an authentic. The fake tag is usually just slightly smaller.Also, the fake tag is not as smooth, like it's grainy... if that makes sense.
Unfortunately, both of these apply to only if you have the dress in hand and cannot be distinguished in photos. But, in this case, you've got it in hand!

There are other ways as well, but these are the easiest things to check when you have the dress on hand.
Anyway, there is a thread for authenticating:
http://forum.purseblog.com/the-wardrobe/authenticate-this-apparel-53838-67.html
Hope that helps!
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