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The most likely candidates for restoring Victoria would be Amy or Bonesaw, either of which would be capable of de-powering her, intentionally or otherwise (Contessa did it with a bullet after all).
My guess is Amy. Intentionally de-powering Victoria seems like an odd choice unless she specifically requested it, which she might have if she wanted to get away from Cape Stuff. That said, she's seeking out cape-stuff info and doing a cape-stuff job, so that seems unlikely.
Alternatively, her powers could still be recharging from the GM. I'm not sure how much I like that answer though, that sounds like WildBow just has a convenient button he can push to switch from Unpowered to Super-Powered mode.
OR, plot twist, she's actually Amy Dallon, having died her hair and taken her sister's name for some bizzare reason. That doesn't fit with a lot of the stuff "Victoria" has been saying about being aware of her body.
My personal theory is that Victoria DOES have her powers, but she's not using them. Specifically, she hates the idea of using her Charisma Aura, between what that did to Amy (and the consequences that led into), and the experience of being controlled by Kheprii, she's rightfully disgusted by the thought of using any sort of mental manipulation power. By suppressing her Aura, she's also suppressing her force field, with the associated flight and superstrength it provides, giving no ground to her Passenger.
Potentially, she had Amy depower her post-GM, if it's not so much Cape Stuff she wants to avoid, but her specific powerset.
As for the golden cityscape, it sounds like that's just a side-effect of using a lot of solar glass, which makes a lot of sense for this new megalopolis assuming they were able to get the infrastructure to mass-produce the stuff.