Interesting that the younger sister is the kind of straightforward, pure-hearted, norm-defying heroine we'd see in lots of regular shoujo or shonen: How dare these selfish rich nobles spend money on frivolous art parties when poor people are starving! etc etc, while the older sister would be the repressive arrogant jerk who only cares about wealth and power. But here from the older sister's POV we see the social deal-making and politicking that goes on behind the scenes: the older sister sucks up to the duchess, in return the duchess donates even more of her wealth to the charity event for poor people, everybody wins. Of course the duchess still kinda sucks for not just giving the money to charity without first requiring an expensive fancy party to flatter her ego, but that's wealthy nobility for ya.
Anyway, this is an interesting perspective flip so far. I don't hate the younger sister because neither she nor the older sister are "wrong," exactly; it just depends on whose POV the story is being told from. But it'll be interesting to see if the older sister's POV actually does anything to address the younger sister's points about imbalance of power in society, or if this story just turns 180 into the simplistic "Rich noble people are benevolent and accepting your assigned societal role is good, actually."