She remembered what it had been like, so many years ago to have been alone on Titan with Tony, to know she had lost her sister, half the universe, all the hope she had of ever stopping Thanos. It felt like a victor was so far beyond their grasp that they would never find it. And yet they had, after many years and at great cost. To see the look on his face as he realized that they had won, it mirrored the emotions she'd felt that day as she watched Thanos and his army disappear.
She wanted to correct him, to deny how good it had been to have that victory, but she couldn't - they both knew that they would never come away from Thanos without losses, but that they had won was the important thing.
"Yes," She nodded, it was something she had not thought to hope for and yet it was her new reality. Gamora was alive, not again, this one had never been killed, never sacrificed for the soul stone. It had been Natasha they'd lost, Nebula hadn't learned the truth of that until after the battle had ended and they had taken stock of what they'd lost.
"She's from the past, 2014." She was not quite the sister that Nebula had lost, but near enough. "We had to travel to the past, Thanos and his armies," Including her sister, "followed us back. She disappeared after the battle."