In Sentence 3, what does “She had two sisters to be benefited by her elevation” mean?

The sentence in question immediately follows the two sentences explaining Maria's elevated social status as a result of her marriage. This is the only type of elevation that makes sense in context, as the passage does not discuss physical elevation (height above sea level) or moral education. Nothing about the sisters receiving dowries from Bertram or about Maria's lack of generosity can be found in the passage.