It's not the second Noi. It's still the same one we know and love. Her memory loss and Astrolabe's error are connected. True Ending will explain it nicely for you.
As for that...."thing", it's fake Zext. Should be obvious from how it appears and why it has Zext's body as the core.
And Wyrd, if you hate Creha's character, you'll hate some villains from Ao no Kiseki, then. One actually has a good goals, but chose wrong methods because he's too reliant to his evil *beep*. And another one is like Creha, except that she's actually understand what's really going on with the world, but voluntarily sides with the villain because they're after her power and she wants to get rid of it ('cause it make her suffer).