For all her money and rank, Anne de Bourgh certainly is lacking when it comes to the social graces. Yes, she is rude to keep Charlotte outdoors on a windy day -- and I am particularly struck by her behavior when Lizzy and Maria and the Collinses come to visit while Darcy and Fitzwilliam are there. Anne doesn't speak to anyone -- not even the cousin to whom she is supposedly engaged, and who seems to be ignoring her as well. While Lizzy and Darcy and Fitzwilliam are talking, she doesn't join in. She probably hasn't been out in company much -- we were told earlier she wasn't presented at court because of her health, and I am sure she's never been to a ball in her life.
She would have been a brilliant conversationalist, had her mother allowed her to get a word in edgewise.