Factual error: When Ed and Lorraine Warren are trying to convince the lawyer to represent Arne, there are is a copy of "Jonathan Strange and Mr. Norrel" on the shelf behind them, which was published in 2004. The film is set in 1981.
Audio problem: When demon Bruno comes crawling towards Arne, the jumpscare sound comes earlier than we can see the demon. (00:24:05)
Factual error: The girl in Ed Warren's hospital room is wearing a UConn sweater with the wordmark from their 2013 logo rebrand that had not existed anywhere near 1981. (00:21:30)
Chosen answer: She's basically a witch/occultist. She uses magic and curses and whatnot, which might explain why she seems to be able to do unnatural things. But she is most definitely alive and not a ghost.
TedStixon