She keeps repeating this, which indicates/emphasizes her frustration about her relationship with Cal.

Jeannine does live in a world that is defined by strict gender roles, and is therefore prudish and modest about sex. She won't even call "it" what it really is.

I think this repetition is really interesting. Isn't she crying already? Then how can she now begin to cry? It's obviously deliberate, but I can't place my finger on what it means.

I think Sarah acknowledges her own personal entropy. In moments of panic, where she "does not choose calm and measure," she is denying herself a sense of order and indulging herself in chaos to get a release. Perhaps she feels extremely trapped as a young mother, or suffers from some other kind of mental illness, but it seems like her willingness to linger on entropy and the heat death of the universe run parallel to her own personal sense of panic and undoing.

Marcel Duchamp was a famous artist, writer, and philosopher associated with Dada principles.

https://www.dadart.com/dadaism/dada/035a-duchamp-cage.html

I feel like this could be a subtle nod, a "wink" as you might call it, to the New Worlds magazine. Just a thought.