"or does this really prove once and for all that spirits and demons exist? You're guess is as good as mine."
The grammar-error was already remarked on, but (slightly) more importantly: Well, no apparently. If your guess is as good as mine, i.e. you declare yourself to be undecided on the truth of this story, it clearly hasn't been proven "once and for all that spirits and demons existed", now has it?
Still, if my guess is as good as yours, I'll just give you mine: Pretty sure this is bullshit. That whole wall-walking bit seems highly similar to that most famous fictional exorcism story you mentioned. And while I agree it made for a nice creepy image to have a demon-possessed child walk across the ceiling, I gotta ask: Why? What are the demons supposed to get out of all these petty tricks? What possible use is it to satan to make a child walk on walls or babble in strange languages. That'd only make sense if we assume god is such jerk he'd send you to hell for actions the demons possessing you performed.
And add in that the people telling this story for no-ulterior-motive-no-really are getting famous and rich by selling movie rights... yeah, I'm gonna need a little more convincing.