The point is that it doesn't matter if the 1922 rules can be changed, the public won't care, you can't keep playing the same trick over and over again. Even if they do change the rules and pot her, it will not make much of a dent in the polls, in fact it may harm them further. It was nasty enough last time, another leadership election would just seal the deal.
The only real way out of this is for Labour to propose a VONC and enough Tory rebels support it or even less likely the party actually splits, with the rebels attempting to start with a clean slate (actually now I think about it, this scenario is the most likely)