I think it's extremely important that there are two Bingley sisters in the novel! By this they form a majority, they represent society and common views, as those give their snarky opinions, quite more powerful as if it was only one sister! "The (fashionable) world" looks down on the Bennett family...
If you have only one sister (as in the 2005 adaptation) she's just one silly snobbish bitch (ignore her!).
Pride and prejudice | Jane Austen




















