he never calls her anything except 'Madam' to her face, but you hear him whisper 'Take Anne, she's very tired' to Sophie. However, he does not use 'Mrs Charles Musgrove' to refer to Mary, so the effect of the juxtaposition of that and 'Anne' is lost. But I guess this is one of those things that is so outside our normal experience now that it would just puzzle most people if they had done this.