Re: (Real) cases of exorcism.
Personally, I do not think there is any way to justify the choices that were made in this particular case.
My observations about people doing things which seem incomprehensible because they are desperate did not directly pertain to this situation.
What is curious is that the girl herself thought that she was possessed.
I believe this small yet important detail as been overlooked. I haven't any idea how the so-called facts were presented in the film, but according to the first link I shared in my last post on this thread, Anneliese Michel was personally "convinced" that she possessed several demons, among them Adolf Hitler, Lucifer, Nero, and Judas Iscariot. It would sound to me as if she would have made a choice to be exorcised independent of the coercion of others. She also refused food and drink. While I agree that institutionalizing her and feeding her by force would have been a very sensible option, we still must admit that these choices I mention were, in fact, Anneliese's own. She was merely strongly supported in the choices she made.
"All men have the same defect: they wait to live, for they have not the courage of each instant.
Why not invest enough passion in each moment to make it an eternity?" ~E. M. Cioran