Guilt
Winry knew that Ed didn't leave her there, in the midst of the abandoned battle scene and rubble, because he wanted to. In fact, she could very well see the guilt in his eyes when he wrapped his red jacket around her still-trembling body. "Winry, Al's still fighting, so..." she quieted her sobs so Ed could finish, "I have to go," she knew this, "I'm sorry." she was, too. She was sorry because even though she knew that Alphonse was fighting Scar and needed his brother's help, she wanted Edward there, with her, she needed him and it made her feel guilty to want something that was so selfish. She decided not to fight it and let him go, choking back more tears, she quietly asked herself, "How come all I can do is wait?"
