I’m saying that the character is made by the author, so she’s not real. She can’t be treated like a real person, because all the choices she makes are chosen for her by the author. So I’m trying to say “Cleo” isn’t trying to excuse her choices with the trauma from her sister, or redeem herself. You don’t have to like her, or feel bad for her. That’s not what the author is trying to do, they’re trying to give the consort depth in her personality so she won’t be boring. And personally, I think the author’s choice is good because usually female villains are just there to make the fl look better as a contrast, but Cleo is her own person. Even if she’s a terrible person. Idk if you noticed, but the double standards for female vs male villains are crazy. Villain men are seen as hot, charming, their evil attributes make them so desirable ("if evil, why hot?"). But the moment it's a woman doing it, she gets jumped.
It's not that villain men are praised while villainesses are hated, it's more like villainesses and crappy ML's are hated. Male villain's flaws aren't paid as much attention when there's already a crappy ML with glaring flaws... bc then it's the crappy male love interest's bull that gets all the reader's focus, and I've already said my piece about this "ML.
As for me talking to the character, lol, I'm not thinking it that hard... I save my brain energy for worthier endevours... But if I really have to say, I'd say this doesn't exactly give the character a real "depth", it only provides context for how Cleo has always been such a petty minded person. She evidently doesn't think that deep, otherwise she would've realized WHY her sister was unhappy even though she had everything and was already "oh so perfect". She completely missed the point that no matter how "perfect" a woman was, in their family, she was still a "men's doll" controlled by the men in her life, if she lived her whole life trapped having to please men much less competent than herself, while never even receiving from them any real love or affection... Her sister simply saw just how small minded Cleo was always being, too trapped by the obsession of her petty, inferiority complex, to ever be able to see the "bigger" picture... of how her being so obsessed with being "more perfect" than her sister only served to perpetuate the roles that women like them were being forced into, and thus only truly benefitted the men controlling women from the shadows... Her petty inferiority complex blinded her to all of that, and ap´parently it still blinds her to it, to this day... So maybe the sister forsaw how she'd spend years just like this, a "men's pretty puppet", and that's why she mocked her. So no, I don't think this backstory helped give her "substance"... it only served to show how disappointingly small minded she is. Disappointing.

Riiiight... bc the kid you abused, now turning the tables on you, has just the same cruel face as the older half sister who abused you. Riiiiiiiight, they're oh so "identical"!! ...NOT.