When I first read it I thought she may have meant to type demilled, then I remembered that she's the most intelligent person in the world so she wouldn't constantly make such a spelling error.
I finally decided to run it through the database on the fictional spirit-guide HQ's computers. The database has every language known to man. Past and present.
The only instance of the word was found in a rare ancient Mayan dialect that was used by a small portion of the Maya empire between 1300 AD and 1425 AD.
The rough translation into English is: I am a babbling idiot, but I pretend to know everything with much condescension.
So I guess that whenever she says 'demiled' you should replace it with 'I am a babbling idiot, but I pretend to know everything with much condescension' in order to get the complete understanding of what she means. I haven't personally tried it yet to see if it fits.