@gronkle: No, seriously — they never seem to care even slightly about anybody other than themselves. Not just “we only look out for each other”, they even treat each other like trash. It feels like one of them could get run over by a car and the other two would run past the mangled corpse laughing.
@ZeeVee they might be frivolous, inconsiderate and self-obsessed at times, but they are kids and that's how kids are. They are the centre of their own universe and everything is abstracted into a joke or a game.
Also did you read the chapter Three People Four Legs? They do care about each other really, when it matters. But they're also good enough friends to make fun of each other quite mercilessly.
@ZeeVee You *did* see that the plot of this chapter involved two of the girls helping the third overcome a problem that had nothing to do with them, yes?