I stand by my description of Mme. Armfeldt's character as I feel it's written, but I guess I was referring to refinement in her manner of speech more than the content of it. Yes, I think she is willing to tell it like it is and use earthy language when necessary, but I would never use the word "vulgar" to describe her. I wouldn't even describe the line you cite ("Don't squeeze your bosoms against the chair, dear. It will stunt their growth.") as especially vulgar, just candid and straightforward.
When I referenced good breeding, what I meant (and what I should have written) was that I think Mme. Armfeldt was well-trained to be a successful courtesan -- a la Gigi in GIGI. At one point in the show, she objects to her daughter Desiree's "sloppiness." I think we're supposed to see something of a contrast between Desiree's "sloppy" lifestyle and romantic life on the one hand, and the way in which her mother lived her life on the other -- far more structured and refined, even though she was a courtesan. I really don't think Mme. Armfeld was meant to sound like a crusty, gravelly voiced, caustic old lady from the midwest, which was how Stritch played her.