Anna was so confident that she could get Stuart to fall in love with her because, for so many years, Stuart had not had any female friends. She was the only woman who could get close to Stuart except for Marina. She never had any opportunities to be alone with Stuart because of Marina.
When Marina had the accident, Anna thought that her chance had come, but what she did not expect is that because of Marina's mishap, it made Stuart more cold and unfeeling. He blamed her accident on himself. He wrapped himself up with self-blame and guiltiness. He no longer accepted anyone in his life.
Anna tried in various ways, but nothing worked. The only thing that made her feel a little better was that she knew that although she couldn't be his girlfriend, he was never going to be with another woman again.