It's really gross to think about and I don't think the people who drank the woman soup should be considered cannibals because they did so unknowingly, but technically what they were engaged in was an act of cannibalism. Of course this leads to another question, is it still cannibalism when you don't know you're eating or drinking human flesh? Technically yes.
The real question is, was the dead body juice diluted enough by fresh water. If it's diluted enough then that would be like drinking pool water with a turd in it. It's gross, but technically you're not really drinking poop. The problem is the guests have reported that the water was "black" and tasted "funny" and they kept on drinking it and using it to brush their teeth, so that's pretty much a bad sign. I wouldn't personally consider them cannibals, but drinking corpse soup definitely does walk the thin line there and all of our sorries go out to them and the lady who died.