Faye's past and her character development. I still find it interesting that Spike is the one who hears her telling Ein about her past. Although he says her "story needs editing," he is just being his normal, rude self. If he were honestly bored with it, he wouldn't have listened to it all. Spike almost understood how Faye felt, being in love and losing it, but he would never show it.
Spike did not think Faye would let Whitney go, and he was right. He did realize that she might take the bounty for herself, but he could hear her conversation with Whitney in her spaceship: all she wanted to know was more about her past. Spike just used it as an excuse to shoot at her, plus, he thought the bounty was bigger than it really was.
In the end, Whitney really had fallen in love with Faye, and she knew this when he said it was another lie. This gave her some sense of satisfaction, but she did not love him now. She just wanted to know about her past, and he could not give her answers, so she stopped caring. But she will remember him as a man who made her who she is now, and that, I think, she will always value.
Also, when Faye is escaping from the hospital and a ship goes whizzing by, it looks very similar to the hammerhead. The writers wouldn't do this on purpose. If Jet had stopped, what would have happened to all of their lives would have been very different. But it did not happen that way. Faye had to suffer for awhile to become the awesome person that she is now.
