It struck me as I read chapter 1 how little we know of Lady Elliot. Lady Russell sees Anne as the enbodiment of her mother.
As I reread the description of Lady Ruseell's first dealingswith Wentworth I am struck how it was not the money issue for her , which I had always thought of being the major barrier, but that she saw Anne throwing away her life on an undeserving man like her mother. He was certainly a much cleverer man than Anne father; but as the text says "Lady Russell had little taste for wit"
So Anne had better judgement than her mother and, though Lady Russell definitely valued Anne more than her family, ady Russell still underestimated her.