Here is a Flemish tapestry, c. 1510-1520 ( http://www.pdl.cmu.edu/Fates/
), of the three Fates. Clotho is the one who spins the thread of life. The others measure and cut. The lady at the bottom suggests that the allegory is the Triumph of Death.
When Adam delved and Eve span (and none then was the gentleman), they were also fated to die, unlike in Eden. The spindle is perhaps a visual reminder of Eve's former belief that if she disobeyed God's orders she wouldn't die. Now, due to original sin, all are subject to this fate.
For the connection between Eve's labor and the Sun of the Charles VI and BAR (Beaux-Arts-Rothschild) cards, there is perhaps Eccles. 1:2-3 "...vanity of vanities; all is vanity. What profit hath a man of all his labor which he taketh under the sun?"
All this has nothing to do with the PMB Moon card that I can see. It does look like cords hanging from her waist, similar to the way monks are sometimes portrayed. But its odd configuration also suggests a bow, bowstring, or perhaps reins. There is also the question, whose bow? Petrarch talked, in his Triumph of Chastity, of Chastity tying up Love and breaking his bow. The engraving in Kaplan, vol. 2, p. 144, shows the pieces. But there Chastity looks triumphant, not sad (detail below).
The PMB Moon-lady might be hoklsing a broken bridle, missing the bit that goes in the animal's mouth. The bridle was a symbol of "chastity, temperance, or Nemesis," G. F. Hill tells us, expounding on the medal shown below, done for Elisabetta Gonzaga c. 1502, probably on the occasion of her husband's death ("Eight Italian Medals," Burlington Magazine
1909 p 215, an article that Huck drew to my attention on another thread). The closed gate behind the lady on the medal means much the same as the bridle in her hand.
The virgin Diana was a goddess of chastity. Thus Elizabeth I of England was identified with Diana; and in the play attributed to Shakespeare, when the virgin Marina prayed to Diana after being sold to a brothel, the Bawd could say to her, "What have we to do with Diana?" (Pericles
, 4.2). A broken bridle would mean no restraint on the instincts, i.e. a defeat for Diana. A broken bow would be similar. Reins might indicate an animal that escaped. Hence the sad face on the PMB Moon-lady's face, which I do not think reflects incompetence on the part of the artist (who, some supposed, was asked to do a card that celebrated marriage but got it wrong). Waist-strings dangling might also suggest that the Moon-lady was pregnant and hence needed a loose-fitting robe. Diana was the goddess of chastity, but just in case, she was also the goddess of childbirth. But I am just guessing.
I do not think that the idea that the sad face indicates the luminaries' defeat by Eternity applies here, as the scene on the Sun card looks perfectly happy. But it could be the defeat of the present generation by the one following.
Another idea: the PMB Moon card might be memorializing girls who had to surrender their virginity in marriage too early, before their bodies were large enough to handle giving birth. Marriage was even at a more mature age a risky proposition, in which women always had to be willing to give their own lives for the sake of the next generation (shown in the Sun card). We see that risk in the precipice below the Moon lady. The designer of the card (whom I imagine to have been Galeazzo Maria Sforza) might have had one particular girl in mind (also for the two cards before, Temperance and Star), notably his sister Elisabetta, married at 13 and dead at 15. Diana could offer her no protection.