I'm sorry to burst your– bubble, but I'm afraid Dulcinea is more likely a direct reference to Dulcinea del Toboso, a fictional character within the fictional world of Miguel de Cervantes' classic novel Don Quixote. She is the imagined damsel in distress that Don Quixote wants to save and then wed, nevermind that she was invented by him and has no plans to begin existing anytime soon. From Dulcinea del Toboso then emerged the French word dulcinée. Vulgarly, dulcinée means fiancée, bride-to-be, or even bride/wife. However, in the abstract (and owing to its literary origins), one's dulcinée is the woman that, from one's perspective, one ought to save or ravish, and then wed as a matter of course (falling in love preferred but optional). The dulcet etymology is of course correct, and I suspect Miguel de Cervantes had much the same line of thinking when he came up, but I have every reason to believe Muir was referencing the character directly rather than its Latin roots.
Now circling back to Don Quixote, the novel was a satirical spin on the courtly love (or fin'amor) genre of literature wherein a noble knight spends ungodly amounts of time pining for "his lady" (his dulcinée, one might say). Said lady is usually already promised/wedded to the knight's lord; and the knight's love is thus never meant to be, nor will the knight ever attempt to do anything untoward– well, towards his lady. In lieu of courtship, which would be tantamount to high treason towards one's lord, the knight will set out to accomplish nebulously defined exploits, which he will dedicate to his lady– or better yet, to his lady's honor, in the hopes that she will notice him, so to speak, and acknowledge his love (which is as frisky as it gets before polite society begins to frown at the noble knight). The knight will then ideally die honourably in quest or combat with his lady's name on his lips. As mentioned, actually courting one's lady is the biggest taboo there is in fin'amor – although stories like Tristan and Iseult suggest that this ideal of the pure courtly love might not have been all that and a bag of potato chips – given how jovially that story shatter that taboo by having the knight actually court and win the heart of his lady, whom in turn cheats on her husband (which is way more agency that a woman ought to have, thank you very much).
[Aside within an aside within an aside, but since we're in good company, I want to point out that Tristan and Iseult is almost surely the blueprint and whole root cause to that trope wherein a lesbian knight wins the favour of her lady (and oftentime gets to have raw euphoric cataclysmically cathartic sex as a reward) after years and years of emotional repression and pining and dedicating exploits and feats to her— now where did I hear all this again? OH RIGHT, FRONTLINE TITTIES OF THE FIFTH (still not a real publication).]
Friends, It is with no little dread that I break the news to you: cavaliers and adept pairs are spiritually French. Cavalier (french word meaning horserider and often conflated with chevalier– literally knight) and necromancer (no etymological link to lady, I'm afraid) are to form a pair wherein each person works for the other, and both people work as a whole. A delicate balance of love and affection and mutual respect and fusional codependency in which romance and sex are taboo. From what we know, Marta was the perfect cav, and so would she have been an exemplary fin'amor knight. Judith, ironically, is the secrelty immensely horny lady of the lesbian knight trope (the juxtaposition of which makes that pair particularly delightful). Camilla and Palamedes are straight from a milder variety of lesbian knight trope, and Gideon has no regard for courtly etiquette, but she makes for a very solid knight protector (not fin'amor tho, not towards Harrowhark), not that Harrowhark is much of a lady at all although they both score full points for repression. It's no always so straightforward as to be a one-to-one equivalent, though: whatever the Third or the Eighth have going on is not like to fit in any permutation of any of these archetypes anytime soon, so let's not jump to conclusions.
Let us, however, finally pay off this whole setup: under this lens, what archetype would Dulcinea be? To whom? What would Cytherea be? Here's my take:
To Dulcinea, Palamedes is her Tristan and Camilla is her noble knight, maybe her Tristan also.
To Camilla, Dulcinea is her lady, no questions asked.
To Palamedes, Dulcinea is his dulcinée.
To Gideon, Cytherea is her lady, and they make for the perfect fin'amor pair on the surface, but in reality... Well by now you surely get that "Dulcinea" is her very own Dulcinea del Toboso.
Sorry for making y'all learn French literature