Dress for a wedding help for my little sister

[massistar]

I lurk a lot on S&B but haven't posted till now. We have a big family wedding coming up and my younger sister is struggling to find a dress. I know that she doesn't have a big budget and really want to buy her a nice dress that I can send to her as a surprise. We live 400 miles away otherwise I'd just take her shopping and do it!

She's a totally different size and shape to me so I really don't know where to start. She's a 16 and around 5 Ft 4 with big boobs and nice legs. She's 30 and blonde.

Hope all you wise ladies can help me out :-)