I imagine her as someone that drinks in secret and then publicly shames anyone who professes the "love of drink." I think she has a bottle stashed away somewhere on a mini-golf course in central park. She goes there late at night, drinks and then stares wild-eyed at her moon, dreaming of the day when she and Clive can be alone there.
I also think that when she was just a girl, she got pregnant and her family sent he to a nunnery to bring the baby to term. She was forced to give the child up for adoption and return home to her friends and family and pretend like she was "away at camp." Clive was the father, though even he never knew that she really wasn't at camp. What?
That would explain why she's got that odd maternal streak towards the Radium Babies. Damn it, man, you should be writing the next one! Or at least doing "Mrs Cholmondeley: The Album". That said, I have a mixtape somewhere I made for the novel. Mrs Cholmondeley's song is Ginger Geezer by Vivian Stanshall — a great, overblown, eccentric bombast of a song. Perfect.