I have read many Villainess regression mangas, but I find this one quite disturbing. I understand revenge and enjoy many with a good story, but this one is just twisted.
1) Past FL is absolutely stupid and therefore was lead to a tragic death, so maybe she deserves a regression, but to do the same things and victimizing Mielle in a similar way (seeing how a motherless Mielle was brainwashed into victimizing FL) makes her pitiful and deserving of a regression too. The real evil was Mielle's maid Emma who being an adult raised Mielle to despise others based on status. Children are impressionable, their personality - an outcome of their surroundings and upbringing, so the major fault of Mielle's twisted, entitled nature falls on Emma. That's why, I actually thought Mielle's delusion during her execution - where she imagines a parallel universe where the 2 sisters are happy together was the best future, according to me. It's ironic how the apparent evil villainess Mielle saw her folly and wished she had accepted Aria shows a profound character growth even in the final moments of one's life, no matter the futility of the situation. But Aria thinks that such a future was impossible is absolutely stupid and hateful of her. The truth of the matter is neither Mielle nor Aria put in ANY efforts for that beautiful future where both could be happy together as loving, caring sisters. But if Mielle could get a regression, I see the possibility of that beautiful future (BECAUSE of that final realization) but Aria didn't do that even after being regressed. BECAUSE she doesn't want that future. Usually people say, when a person dies, all the bad blood is washed away and they wish they could have been friends instead. But it's pathetic that Aria doesn't think so but Mielle did at the end.
2) I hate both Mielle and Aria. Both are psychopaths and sadists which are unlikable qualities in any FL. Mielle is selfish, self-centred, manipulative and evil and therefore is hated as the villain. But Aria having these same qualities but portrayed as the FL is absolutely hypocritical.
3) Aria is an ungrateful B* - she only sees how the count gives undue credit to Mielle (which I hate him for ofc) but ignores the fact that he was the one who showed her mother kindness and took not only one but both of them in - to the point of going against the accepted societal norms of the nobles. As one having masters in English Literature, I don't remember any noble family of those times in any part of Europe marrying a prostitute! That's just unheard of! It's a huge deal. But the author, this manhwa and even the readers just gloss over the seriousness of this fact and the social stigma that the noble family can face due to marrying a prostitute!
4) The unnecessary addition of tropes like childhood friends, finding long-lost relatives or birth-secret/unknown noble lineage is just stupid because it does absolutely nothing to change Aria's evil personality. The author just added additional perks to show Aria as above others, which personality wise, she's the lowest of the low.
5) Aria's lack of understanding wrt Mielle. The author shows Mielle as this typical one-dimensional villain hell-bent on downgrading Aria and aspiring to become Oscar's wife. Apart from these 2 sides, we don't see any of her life, HER STORY. So to my question - can Mielle be saved, the answer has a huge question mark because we don't actually know, and whatever we know is what the author puts forth as a justification for Aria's revenge story. So even though Aria knows that Emma is the puppeteer behind Mielle, she doesn't try to change Mielle (even by manipulation) into a redeemable character - even just to use as a pawn like Annie. She's so bitter that she wants a fellow villainess in the form of Mielle. Furthermore, she wants one villainess to win at the expense of the other. Which is just twisted.
Until the end, she doesn't spare a single thought (forget about regret) for the 3 Roscents' tragic deaths. We saw at the end that Cain was actually becoming a good character, so why kill him off? Just to drive Mielle insane.
Conclusion: This story has lots of holes especially wrt character stories. I've similar opinions about other main and side characters. Aria is an unhinged psychopath FL. She lacks basic human compassion. I absolutely hated her character. Prime example of "Evil Beauty". Such people only know how to use others for their own benefit, and no one likes such people irl, irrespective of their backstory.
There are people who might not agree with me, but that's ok. You are free to like her, just like I'm free to dislike her.
Note: This manga is a good topic for analytical review.