I think the notes at the end of the chapter are wrong the dialog indicated she had a slight demon aura because she used their technique (probably the one from the creepy kid?) if she was one herself such a reason wouldn't be necessary.
@Ibri Problem with that is the snake-like brat said the skill wasn't suitable for him because his body was different. It's clearly implied that the skill is for humans while he's a demon, making it incompatible.
