While I actually do believe in the existence of spirits of all sorts, including what one might call "angels" and "demons", what is being described here sounds like possible signs of schizophrenia rather than demon possession.
I am a "fallen" Catholic myself. My experience with Catholicism was nowhere near as negative as my experience with people from sects such as the Church of Christ, or certain more extreme Baptists. However, I cannot agree with dogma that dictates that homosexuality is a "sin" and so is birth control.
I discovered the real "Old Time Religion" in my late teens. (Translate: I became a polytheistic heathen.) But it would take years before I stopped having dreams that I would burn in hell for my "evil" decision.
There is good and evil, and this applies to purely spirit beings as well (i.e. angels and devils.) But I think the case of Annaliese Michel is the story of a misunderstood young woman with a serious and improperly treated mental illness, not of actual demonic possession.
One might argue that the mental illness made Annaliese more vulnerable to demonic possession. But even in this case, proper treatment of the psychosis would make her stronger and more able to fight off such attacks.
