There are dozens of articles that refer to Beulah and probably hundreds about her father, Robert W. Logan, and also her mother, Mary Fenn Logan. I have a huge collection of them and I could easily double it. It wouldn't surprise me that a missionary would make up cannibal stories but, in this case, I wonder if there wasn't some journalistic exaggeration. Beulah could not possibly have misrepresented the date and circumstances of her father's death and gotten away with it - it was very widely known that he had died a martyr in 1887; he was a hero in missionary circles. There were many lengthy articles and eulogies about him published at the time in newspapers and missionary magazines. Unfortunately, though, I can't track down any other report of the goings-on at that Methodist camp meeting in 1906 to verify exactly what she said.
I agree with KGarrad about the total improbability of the story. Reliable reports of cannibalism are almost nonexistent. If Beulah and the crew actually witnessed such events, it defies belief that no report was made to the authorities when the boat docked in Australia but I can't find any contemporary report in an Australian newspaper. She arrived there in February 1900 but there was no mention of this horror story until 1907 when the US article was reproduced in the Sydney Morning Herald.
As for the finger, I'm more inclined to believe that story. Certainly I have several times known similar cases here in South America of thieves stripping valuables from the bodies of the dead and injured. Wrenching or chopping off a finger is not unthinkable to me. Too bad I have no photo that shows Beulah's hands. And too bad, also, that I was uninterested in Beulah or any other ancestor when I was a child and could have gotten the lowdown from grandma. The only anecdotal note about Beulah that she included in her little written summary of her family's history was that, as a result of the shipwreck, Beulah had almost entirely lost her voice but that she was nevertheless a very popular public speaker because people liked to look at her even if they could barely hear her.