I'm not really engaged with the premise given that it's yet another "enhanced human supremacy dilemma" story, which is pretty overdone in the Gundam franchise. With Mari's apparent death though, I'm truly curious as to who or what the girl from the start of the story is.
Also given how far along their relative timeline the story takes place, I wouldn't be surprised if the universe had medical nanomachines a la Gundam 00, and she'll be placed in a restoration chamber for some period of time.
All that said, I don't understand why the governing bodies didn't merely cover up the existence of "Eights" or introduce them as a Space-Exploration spec model of the existing 7th gen, so as to ease potential tensions. Did they not have a protocol established through the introduction of previous generations of humanity? Was there never dissent between previous generations of humanity? What makes this scenario any different aside from the space expidition?