I am having my five bridesmaids wear Alfred Sung styles and they all have very different body types, including some plus-sized BMs (both are usually around size 16, but the one who recently had a baby when we tried dresses on was a 18-20).
The samples were a little small for some of the styles, but in general they still looked pretty good on them. I must say, though, the ones with the pleated skirts are more flattering than the bunched skirt.
Also, I had a friend try on the Alfred Sung dress that is similar to the one your younger sister wanted to wear (with the ruffled collar), and it just looks ridiculous and unflattering. It looks great in photos, but it is definitely not
Would you be against having your BMs wear a shrug or bolero? It would make it easier to find something a little flattering. We found that the most flattering Alfred Sung style was this:
If you are concerned about the price, you can order the dresses online from NetBride or Brides of California/Perfect Bridal for a much better price. I personally am ordering from Perfect Bridal because I live by their actual store.