What if the body "spasms" every few minutes? Go in, say "move" and soon thereafter, she "moves."
Could it be that brain death is not a simple binomial issue, a "0" or a "1" for dead or alive?
I don't presume to know the biology, science, chemistry, medicine about it all.
In the case of my family, and my wife's family, we don't intend on leaving people on ventilators and feeding tubes to keep them "alive."