So why is Maxi’s appearing again? She’s never been one to care for Maxi. Makes me thin...

We don't really know that? For all we know they couldve been forcefully isolated from each other and her sister would've also been receiving the same abuse albeit in different ways. She was trying to survive just as much as maxi was. There's barely any mention of her

Yeah, I'm with you on this idea. Being an emotionless husk is another sign of abuse. And because she was the "golden child," it meant he took Maxi's failures to vent any frustrations about his other daughter out on her.

Rosetta likely doesn't want to marry the prince for any other reason than escaping their father. If this marriage collapses, she will remain in his abusive hands. If she had any ill-intent towards her sister, she wouldn't have left Riftan in and smoothed out their escape.

Because even if she wasn't beaten as a child, she could have been even after doing everything perfectly once Maxi wasn't there anymore. And a failed marriage was confirmed to be a beating sentence. Rosetta was always going to be able to escape; Maxi would have been doomed to be there forever if she had had a brother to take her father's place in the war (because as long as he's safe, I bet he wouldn't give a rat's *ss about sending any related male out in his place.)

That duke will never be satisfied with anything in life. He needs to die in agony, whether it is what others consider it or what he perceives as perpetual agony. Rosetta will survive as she always has. The whole long game of the story is seeing if Maxi and Riftan can get over their own pain to achieve the happiness they deserve. If they can do that, they'll have the best life out of those that came from that castle.

Dont be too harsh on rosetta.
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She was also abused by the duke. The duke doesnt want to blemish rosetta so he always makes her watch as he punish maxi so rosetta will be scared to do anything. The 2 sisters were busy fighting for their own survival to care for each other.