Fear shrinks attention down to the last thing you own, and a mind fixed there is only rehearsing an ending.
Panic carries out instructions like a last rite, which is why the terror has to be cut away before any instruction can land. A state of dread can execute nothing but a plan for dying, and a handful of meal measured against a famine will compute the same way every time it is counted.
Serving first is not a tax on the little she has. It is what breaks her attention off the arithmetic, and a mind occupied with another person's hunger cannot simultaneously run the numbers on its own. The prophet gives her hands something to do while the state changes, because a new state held for one act becomes the state in which provision can be received. A person who guards the last handful spends their final days fully occupied with counting it.