At the very least, Charlotte is making a pun (since a woman of her class and era would almost certainly speak French) and it's doubtful Sondheim was unaware of it.
But it isn't likely Charlotte gets laid every day or is talking about her own orgasms (except for the part of the lyric where she talks about her eager response to Carl-Magnus on the rare occasions he reaches for her). Charlotte's orgasms are overwhelming and humiliating, but they are not daily occurrences.
It makes more sense that her husband's daily petit-morts (with his mistress) are slowly killing her. By this scene, Anne believes Frederick has committed adultery with Desiree or would like to, so it does make sense when she joins Charlotte in the use of the term. (ETA but if I were playing Anne, I'd probably assume the pun goes over her head.)
Updated On: 10/24/11 at 07:52 PM