Gamora was prepared to die when their trip to retrieve the aether failed, when Thanos took her and teleported away. She wasn't afraid.
But she took a look at her sister, pieces torn apart, and felt screams clawing at her throat.
"How can you call her your daughter when you torture her?" Gamora spat at Thanos.
"You know where the soul stone is." Thanos said. "Lead me to it or she'll suffer even more."
Gamora stayed silent, and her father nodded at the nearest guard who pressed a button. Whatever it did caused Nebula to shake and scream, the sound distorted and metallic.
Her screams grew louder and tears welled in Gamora's eyes.
She finally broke. "Vormir!" She screamed out. "The stone is in Vormir..."
"No..." Nebula rasped out.
Gamora went over to where her sister hung suspended in the air and touched their foreheads together.
Nebula seemed to find it hard to speak, her voice more artificial than ever. "Everyone... everyone knows that the stone requires... a life."
"A soul for a soul." Thanos said, and placed a hand on Gamora's shoulder. "Luckily, I have one."
It wasn't unexpected. Thanos felt like Gamora had betrayed his love. It would be poetic, in his eyes, to kill their unperfect love for the sake of his true love: Death.
Thanos was nothing if not a lover of poetic sacrifices.
"I love you." Gamora whispered.
"Don't." Nebula protested as she stepped away. She looked into her sister's face and she knew that if Nebula could cry, she would've been doing so right at that moment.
She turned away.
Gamora was prepared to die.
She wasn't afraid.