So much time had passed since Thanos had died, first in her own past and then again in her present. She had started to live as if she was truly free of him, as if she would be able to move on and find a new life of her own, without the shadow of the great Titan hanging over her every move, motivating her in everything she did - whether it was serving him, or seeking out revenge for all that he'd done to her in her life. But seeing this room had set something on her that had left Nebula panicked in a way she had never truly experienced except as a small child, before she had learned that no matter what she'd done it would never be good enough for her would be father.
Cold crept through her circuitry leaving her frozen on the spot and even with Gamora standing between the open door of the room and herself, Nebula could not look away from it, that place where she had been so tortured for so long.
She didn't hear Gamora's reassuring words at first, her focus narrowed as it was, only on the room, only on what would be coming from it. It was Gamora's hand on her that forced her attention to shift, a full body flinch that she'd have never given away had she not been quite as focused on her fear as she was in that moment. But it was enough, to let her hear what Gamora had said - Thanos was dead. She was there, not their father. It was just them, sisters, in a world that had done it's very best to tear them apart and tear them down at every opportunity.
"Gamora," She said again, taking a breath, slowly and taking that momentary distraction to regain control of her body, to not let it be ruled by the fear that still niggled in the back of her mind. "It -" She started and stopped. "It just appeared." She said finally, forcing herself to look at her sister and not the room. "It should not be here. It was not here before and now -" She glanced only briefly over Gamora's shoulder to the room before she shifted her gaze once more so she did not give in to that fear once more.