Inara wears this dress when the Operative arrives at the Training House. We see it for about 5 seconds. :)
More after the break...
More promo shots:
Here are the Propstore pics of this dress...I think. In the description with the pictures, it said it was in a deleted scene. I'm pretty sure this is the dress, but I could totally be wrong. She is totally wearing that bracelet as an arm cuff, though...
My Photobucket Album for Inara.
Serenifly Costumes site for Inara.