I can say with a degree of certainty that Harsgaard, the final boss of Remnant: From the Ashes Subject 2923, is going to kill you. After you get back to earth, you need to fight him, and it is going to be a rude interruption to the bullet-hell style of the final fight.
So, when Harsgaard sends you packing all the way back to Earth to lick your wounds and figure out what went wrong, you will need to make your way back to the fight. If you talk to the NPC right beside the portal at the center of the blast room, they will tell you to activate the portal to go back, but if you do this, you will just be sent to the snowy caverns where you found her.
What you will need to do is head for the strange energy nodule on the wall in the room near the blast doors. Interact with it, and you will then be sent to the other plane of existence. Only then can you use the Portal to get back to Harsgaard. The Portal will switch colors from blue to red, and this is when it will send you to Harsgaard instead of just back to Resium.
Be careful when you go back, as there is no delay to the start of the fight, Harsgaard will start casting attacks and abilities the second you arrive, so prepare to dodge roll to safety if you need to.