Sad to say, I don't think Adam is going to ever do anything to jeopardize Gnat leaving the game.
THE FOLLOWING IS JUST MY OPINION (donning flame-proof suit).
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I think Adam sees in Natalie the trashy hooker type that he's been hooked up with. I'm pretty sure that early in this travesty of a season, Adam said he doesn't date, he just spends money on hookers. I think fake-boobed, drunken Gnat reminds him of exactly the kind of girl he's most comfortable with. And because of this, there is nothing in this game short of her nominating him for eviction that's going to change his mind.