What might save her are:
1. There are a greater proportion of MPs on the Govt payroll now with even a few dozen trade envoys meaning almost half of the Parliamentary Party are in Govt.
2. Most Tory MPs are out of step with the membership and voters. They were Remainers and if they could, would reverse the decision.
They certainly will not want a Brexiteer in charge.
However if May is toppled, a Brexiteer leader is almost inevitable. They will probably agree one candidate. If we get to that point I expect it will be BJ with Davis back in as DEXU Secretary to finish the job off.
I see he has already put out an alternative Withdrawal Agreement today and it seems sensible. It doesn't take us back 12 months, it just seeks to get rid of the main sticking points and keep some options open after 29th March rather than signing them off now.