Naminé was a different type of Nobody. She could mess with the memories of other people. She could even destroy them; break their hearts so they were nothing more than a shell. This made her a valuable slave for the Organization, who were trying to retrieve as many hearts as possible.
Naminé hated her 'job'. She couldn't stand ruining the innocent lives of those who became close to her. Because of this, she shut herself off as best as she could to the world. Anyone who came close to her or even acted polite to her she would act coldly to. It made her come off as rude, but deep down she just didn't want to hurt anyone anymore.
One day she came across a man named Zack. With his cheery and polite personality, he smiled at her and struck up a conversation. Naminé acted no different, glaring at him and trying to shun him away. Feeling awkward, Zack thought she was shy and tried to break the awkwardness with a joke. Naminé, though reluctant to let anyone into her life, laughed and couldn't be mean to him anymore.
Soon after, Zack and Naminé became secret friends, meeting up in a flower field everyday. Zack was Naminé's prince - he saved her when she was at her lonliest. She began to trust him with her life and told him all about the abuse the Organization put her through, about how tough and unfeeling they were. Rage building inside him, Zack wanted to defeat them and free his friend.
As soon as Marluxia, the ruler of the Organization, found out about Zack, he wanted to kill him or more specifically, get Naminé to kill him. But she couldn't. Pretending she would, she told Zack to run away as they were far too strong for him. But Marluxia quickly found out about this too, and pushed Naminé to the floor as he went to kill Zack himself.
Along with his friend, Zack saw Marluxia heading towards them and leaving his friend behind he prayed one last time. Naminé was the only thing on his mind and he had to fight to protect her - even if he would fail.
As Zack fell to the ground in defeat, Marluxia told Naminé of his 'triumph' and she was crushed. She couldn't believe her prince had died and she'd never see him again. All the things he did for her and said to her... she'd never hear his voice or see his face ever again.
Time passes and Naminé was still a slave, but the fact that Zack is gone was killing her slowly. One day, she stood in the castle as the main door openened and a boy walked in. He told her about how he was told to come here by a strange hooded man to find what he seeks and asked Naminé if she knew where his friend was. Shocked to see this boy, who later said his name was Sora, she stood dumbfounded as he asked her these questions until she remembered her usual ways of being cold so he wouldn't get pulled in; this was clearly all a trap set by Marluxia.
Despite trying to be stubborn, she shed a tear. Confused at her attitude, Sora told a joke to calm her nerves. Naminé spun around and for a split second she saw Zack as the image faded away into Sora. Believing her prince has come back she acted kinder to Sora, and as the friendship between them grew she also told Sora about her abuse in the Organization. Sora was furious and vowed to defeat them. But remembering Zack in him (and feeling guilty of being Sora's friend just for that reason) Naminé begged him not to. It took a lot of convincing until Naminé told him she can help find his friend if he describes her to her. Sora remembered this and talked about the most beautiful girl he had ever seen. How polite and sweet and kind and pretty she was and how he was doing everything to find her.
As Sora rambled on about this girl, Naminé began to feel lonely again. Zack never did this. To him she was his perfect girl. Despite feeling horribly guilty she told Sora of the abuse again, and Sora promises to defeat the Organization before finding his friend.
But she had no idea he actually meant it. As Sora went to seek Marluxia and his teammates out, Naminé realises her mistakes and begs him to stop. But this time he wouldn't listen. He wanted to save her, to let her be free. He found Marluxia and they fight, Marluxia furious that Naminé hadn't disposed of Sora yet, as his heart was particularly strong. All the while Naminé begged Sora to stop. She ran off to think of everything she had done, unknowing that Sora was defeating every Organization member he came across, fueled by his rage.
Naminé thought long and hard about everything. Her meeting with Zack, Zack's death, her playing along with Sora's friendship just because she saw Zack inside of him. She couldn't take it anymore. She hurt too many people and thought she had nothing left in her life. And if Sora stayed around, she'd end up destroying him unintentionally. She couldn't hurt anyone anymore. She had to end it now.
As Sora looked for Naminé, all the Organization members defeated, Naminé was preparing herself. When Sora walked to the top of the castle and found her, Naminé immediately put him into an eternal sleep. If he never wakes up, Namine can never hurt him, and maybe she'd learn to stop hurting anyone else, forever.