racer, you are being an irrational Abi lover again.
If Skupin or Lisa were to backstab either Malcolm or Denise, they would lose their jury vote anyway and the whole jury will continue to hate them for keeping Abi over Malcolm and Denise.
And who says Abi won't win if she made it all the way to the end? She's like an underdog and if she's sitting with Skupin and Lisa, whom the whole tribe equally hates, she will be able to get two votes or three from Pete and Artis... she just needs a few more to win.
Sending Abi home was the most rational choice, to get in the good books of the jury and not continue to piss them off, plus keeping jury votes of Denise or Malcolm AND getting rid of an annoying brat.
Nobody flushed down a million dollars by keeping Abi, we never know she could pull a win or not.