You're wrong about River. River's not on the ship. They didn't want her here, but she couldn't make herself leave. So she melted... Melted away. They didn't know she could do that, but she did.
River ,'Objects In Space'
Spoilage Lite: Buffy
[NAFDA] The place for casting and other vague spoilers, for those who merely want to wade, not drown, in the spoiler sea. Casting spoilers are okay, as are non-plot-point specific spoilers (like, "Joss says the theme of Season 7 is ____"). White-fonting is always appreciated. Information from Magazines like TV Guide may also come up.