Cristian, what a fun project! I found
this dress on a Google search for vintage prom dresses...the model isn't exactly "of the period," LOL, and doesn't show the dress to its best advantage, but at least you can see the entire gown if you scroll to the bottom of the page. Your friend will probably have more luck finding what she wants by looking for circa-1950 prom dresses, than wedding dresses
per se. Hope this quest has a very happy ending!

(I think we need a clinking champagne glass emoticon.)
Edited to add:
Here's another confection! The site (Blue Velvet Vintage) includes vintage-inspired and genuine vintage garments (like this one). It's wonderful!