Earlier in the GR, there was a discussion about whether "the elegant ladies who waited on (the Bingley sisters)" were servants or visitors. In ch.56, we are told that Elizabeth notices Lady Catherine's "waiting-woman" in her carriage. To me, this is clearly her ladies' maid, so IMO this is evidence that the "elegant ladies" of ch.9 were the Binglettes' personal maids. It would be just like them to hire "impressive" servants!