Anne is very liberal in her ideas and is certainly less of a snob than her family and many of the people around her--including Mrs. Smith. (Who afterall pointed out the main objections to Mrs. Elliot was that her parents were in trade.) I think there is something slightly tongue in cheek in JA's making Mrs. Smith a bit of a snob in regards to Mrs. Elliot. It adds an extra bit of irony to her current situation, which is dependent on charity and "low born" people like Nurse Rook.

Yet, Anne for her liberality doesn't take notice of servants. Line has pointed out many, many instances of invisible servants in Austen. This is a reflection of her class and time and place, I believe. When servants do have a face and name and character in Austen, they are still very servile to the needs of the main characters in the novel. Mrs. Reynold's gives us vital information about Darcy in P&P. Thomas' trip into town in S&S yields a frightful piece of news for Elinor. Serle and James allow Mr. Woodhouse to exhibit some of his more famous quirks in Emma. Badley the Butler unwittingly weilds a blow to Mrs. Norris' ego in MP and Maria Rushworth's adultery is brought to light by a maid. In the same novel, Betsey, Mrs. Price nemesis, provides some much needed comic relief and she tells us more about Mrs. Price's character than she does of herself.