Did namine destroy all memory of Sora

No, she did not. She changed a lot of his memories during the course of Chain of Memories/Re: Chain of Memories, but she did not totally destroy them. Near the end of the game, Marluxia commanded Namine to shatter all of Sora's memories, but she didn't want to. Although, Namine did remove Sora's memories of Castle Oblivion and of herself while he slept in the flower-shaped pod.