Shelly started to campaign against Jeff and Jordan and worked hard to keep Danielle in the house when there were 7 houseguests still left. I will show why this was her biggest mistake in the game.
First, let us look at how the game might have logically played out at the time Shelly made the move. She was sitting pretty in a solid alliance of 5 houseguests (JJRAS) with one of the strongest players in the game (Danielle) all set to be evicted. Danielle’s departure would have pitted Shelly’s 5-person alliance against Kalia and Porsche in the wake of their mentor’s departure. Even with Jeff out of the HOH bidding for one week, it was a reasonably safe bet that the remaining four houseguests had a fighting chance to keep control against the KP dup who had won very little until that point in the game. It would be a fairly safe assumption that K&P would be knocked out next. That itself would be quite an accomplishment for Shelly to make the final five as someone who had won absolutely nothing until that point.
But Shelly had a fairly good sense that she would actually make it to the final three because JJ would see themselves having a better chance to win against Shelly than against either Adam or Rachel. So, once again, purely by the strength of her association with JJ, Shelly could easily have found herself in the final three under the scenario that had been playing out. Once she got there, she was correct in assuming her chances for winning either the $500K or even the $50K was small. However, given how weak a player Jordan has been, there was at least a possibility that she could beat Jordan in the physical endurance portion of the final three competition and then maybe get past Jeff in the final 2 assuming it was some sort of mental guessing game (remember Jordan won this kind of a competition when it really mattered at the end of her season). And so, even with the chances being quite small, this scenario where Shelly stuck with her 5-person alliance offered her an excellent chance of making it to the final 3 and a small (maybe 20%) chance at the half million dollars.
But that was not to be. Somehow, Shelly thought she could do better!! Now let us see if her head was screwed on right. With her active campaign against Jeff, Shelly would have been exposed as a two-timing schemer and liar, she would have incurred the wrath of her alliance and won zero respect of the remaining houseguests (no matter what they told her). Assuming that she did not get the votes to evict Jeff (and she did not), she would be in no-man’s land with neither side trusting her fully and squarely in Jeff, Jordan and Rachel’s sights. The chances of her being the next evictee were thus vastly improved. The only chance of her making it past one more eviction would be to hope for a KP HOH AND POV win in which case she could abandon sides and make a new alliance with that duo. However, a lot of things would have had to go Shelly’s way before she found herself in the final three with K&P or, if she had had her way, with Danielle and Kalia. In any case, why would her chances to win be any better under those circumstances? Could she have beaten Danielle and Kalia in a final three any more than she could beat Jeff and Jordan? If the answer to that is no, then why trade what is an extremely high percentage final three deal to make an extremely low percentage final three deal? As things played out, Kalia and Porsche did go on a tear and won three competitions in a row. In spite of that, Shelly now finds herself ready to be evicted with five houseguests still in the house.
Shelly also destroyed her reputation not only as a decent person (which was questionable anyway) but also as a game player. She broke her solemn word to her alliance and potentially any chances for a lifelong friendship with Jeff and Jordan (which she claimed was extremely important to her) – and all for what? For an outcome that is much worse than the one she was supposedly trying to change and one that lost her any chance at all to win the game. Bad game player? No. Terrible game player and one of the worst moves in Big Brother history.