On IMDB webiste about the show (link included here) at the bottom it says that Reem Acra provided the wedding dress. While there is no picture to say that its the same dress, there was only one that I can remember.
http://www.imdb.com/title/tt0321018/combined
The wedding dress she wore to her wedding to Guy Ritchie was designed by Stella McCartney.
Ada Athannasiou designed it, and I know this because that was MY wedding dress!
America Ferrera's wedding dress was designed by Amsale's Christos label.
Brooke Davis designed the wedding dress for Peyton in season 5.
maybe it was designed by the wedding dress designer hired by the company or the wedding dress can be bought online .
Vera Wang designed Chelsea Clinton's wedding gown.
Sami herself designed that dress.
Vary Wang is one of them.
The cast of The Old Wedding Dress - 1912 includes: Beverly Bayne as Jennie Lily Branscombe as Aunt Betsy Dolores Cassinelli
The Duchess of Cambridge's wedding dress was designed by Alexander McQueen's Sarah Burton.
Norman Hartnell
stella mccartney