It's simple psychology. This is an entertainment show. The public want to be entertained. Entertainment MIGHT take the form of a contestant who was amazingly good at trials (Martina, for example), so that you'd watch out of sheer admiration. Or it might be because the person taking part made such a massive fuss over it, and did so badly, that it was actually funny to watch. No-one who votes (and I personally don't) is going to vote for Stacey again because she did a reasonable job, with good grace, wasn't scared, and had already scoffed a kangaroo penis, thereby showing that she was up for it. Nice girl, and she may well win, but at this stage the GBP will vote purely on entertainment value.
To those that say voting for GM is playing her "game" - what sort of game is that? Is it the game that says "I'll make myself REALLY annoying and horrible and useless, so everyone hates me and laughs at me, and then I'll go home and I'll get a new career out of being REALLY unpopular?" Don't think that will work. If GM is playing a game, I think she's miscalculated massively, and it will catapult her even further into obscurity and public ridicule than she already is.