Dombey and Son: Chapter 46; Mrs. Richards (Polly)

In chapter 56, why does Captain Cuttle and Susan Nipper propose to seek out Polly as a maid to replace the "daughter of the elderly woman who usually sits under the blue umbrella in Leadenhall Market?" There was no mention in the story of the daughter of the elderly woman being Florence's maid at the Midshipman beforehand, and it was Susan Nipper to begin with who was sought out by Toodles to be brought to Florence to serve as her maid again? Also, there is no dialog in the story as to why Mrs. Richards was assigned to replace Mrs. Pipchin after Mr. Dombey's downfall and all the house staff had left. Mr. Dombey had fired her once. Mrs. Richards just shows up at Dombey's house in chapter 59. There is a story disconnect here, or did I miss something in my reading?