Title here is misleading (probably deliberate). The email that got this person “fired” was one that allegedly contained an ultimatum and a threat to resign. The employer then called her bluff and accepted her resignation with immediate effect.
> contained an ultimatum and a threat to resign. The employer then called her bluff and accepted her resignation A threat to resign isn't the same thing as resigning. And it seems you don't think so, either, since you characterize her threat as a bluff. It can't be both a bluff and a resignation.
If I say "I demand X or else I resign", (I don't know if that was actually said) I think it's fair to consider that a conditional resignation.