What Peggy is used to is being called ‘sweetheart’ even though she's in charge of everyone, and people looking at her like she slept her way to the top, and colleagues' wives asking if she has any children and then smiling at her like she's Tiny Tim when she says no. She's used to people being presumptuous, talking over her (even when they're not saying anything); she's used to battling to be heard, even with other women.
Lee's reaction to her is the polar opposite of that, and Peggy has no idea what to do with it.
“Um,” she says, eyes darting to Michael (still looking at her like she's a horse who just lost him $50 at the track), then quickly back to Lee (who isn't really looking at her at all). “Ginsberg said you're a model in Chelsea, that's amazing. My friend says the art scene there is where it's all happening.”