Even managing to play with the conventions set up in the damn BD extra manga!
wait is this chapter trying to retcon what shio might've originally meant when she said "I'm done with all that now"?
I don't think so, or rather I think it's just adding and not removing the original meaning. She originally told her brother in the apartment complex that she wanted to go with Satou, and to just pass on her gratitude to their mom since she wasn't coming. In the final chapter, she reaffirms that she's done with her family because Satou's still with her (which V11 helps to illustrate.)
I think this chapter just makes it clear that she's
also moving past her thoughts of what could have been if the plan had worked out. She doesn't want a happy life with her mom and brother, and the fantasy she's going to obsess over isn't a daydream of a potential future. She wants to maintain her Happy Sugar Life just the way it is, which was also the core of Satou's wish. In fact, Satou had to break her image of Shio when she wanted the truth, and she accepted that they'd need to leave and build a new castle, while Shio has a Satou in her who'll never be less than her fantasy of her and she's still living in their obliterated castle.
It's an interesting distinction since she's still regressing into a fantasy, but it's one that's more motivational and easier to live with than just pining away about what could have been. Since it's harder to shake, it's harder to imagine that she'll ever compromise it or grow out of it. Her brother's V11 chapter was also about moving forward and doing what you want now instead of living with constant regrets, the idea that he's the one still trying to return to an unwanted status quo while Shio's grown past that in her own unhealthy way is really neat.