Peggy tells Megan, with faux casualness, that she’s been busy and still owes The Drapers a wedding present. She’s not really casual about it, because it wouldn’t still be on her mind unless she felt guilt. A couple seasons earlier, she is quick to buy a gift for the newborn Gene. “Ma” might be a piece of work, but she raised Peggy to be respectable, to not embarrass her with bad manners. Peggy knows all-too-well what is expected of her.
Is there anything that better says “well brought up,” particularly to older generations, than writing a thank-you note, and in a timely fashion? Dawn was the perfect guest, even when Peggy was not the perfect hostess. That, in itself, along with the carefully folded blanket, can be seen as a subtle rebuke. She comes from a good family, she knows about thank-you notes, folding the blanket/making the bed, and her family worries about her as she seeks independence and a career in the city.
That she left the note on Peggy’s purse? Too pointed to be coincidental. She is hurt, possibly angry, and there is nothing much she can overtly say about it, so the placement of the note says what she can’t. Despite Peggy talking about sticking together, and like Hollis and Pete in the elevator, Dawn is in a precarious situation. Hollis and Dawn know that it’s easy for the person with the real power and privilege to say “everyone is equal here,” but that believing that is foolish. This woman has every right to be passive-aggressive in a way that she can deny if need be.
Peggy, because she is a decent person who’d offered the invitation with the best intentions, felt shame within moments of distrusting Dawn, and more shame upon seeing the note. She knows she is still a product of her upbringing, no matter how much she despises it. But the same rearing that made her suspicious of Dawn also taught her to be polite.
Dawn in a few sentences made clear to Peggy that they really do have a lot in common, right down to a way with words and an understanding of subtext.