White diamond in this redesign is much more isolated, even before pinks death, acting like the overseer of the whole empires expansion. Her original form was simply her gem in a cosmic cloud of smoke and light, however her lesser sister diamonds had a more physical form and could not support such a loose form at all times. So she adopted a more humanoid figure while still being made of smoke overtime. That’s also why gems poof when their physical form is heavily injured, as they revert to base form (smoke) which causes them to collapse as their gem is too weak to stay like that.
White Diamond was born as a one of a kind radiant lifeform, her gem was formed in the center of a forming star and for millennia she travelled the universe trying to find beings like her. Eventually she had enough, and decided that if there was no other like her, she would simply have to create them. So she created the two lesser diamonds Yellow and Blue. Though they were imperfect and she saw them as lesser, they were far closer to perfect than the organic lifeforms she had Wittnessed in her life. Still, she wanted a being to be her equal, so while Yellow and Blue started creating smaller gems to spread their forming empire, White began the careful preparation of the final diamonds formation.