I respectfully disagree. The question of whether Jahni is dead or not dead, is, like the question of whether an embyro is or is not a living human being, a matter of scientific fact. People may want to debate it, but ultimately it comes down to observable scientific criteria.
Jahni is dead because she has no blood circulation to any part of her brain and no electrical activity in the whole brain, causing total and irreversible cessation of brain function.
Her mortal remains cannot do anything a living body can do. It cannot do anything but decompose.
This is dreadfully painful for her parents, but they must keep in mind that it is no act of respect to ventilate a corpse until it rots off the table. And it is a Corporal Work of Mercy --- and a moral obligation --- to bury the dead.
Unfortunately we have come to the age where technology has introduced questions/delemas that we never had to deal with.