Why did Izumo's familiars attack her in Blue Exorcist? So I read the Manga and also watched the anime. There is an arc in the Manga that is not in the anime, the Illuminati arc where Izumo is kidnapped and taken to the Illuminati lair. 

Those fox spirits, even if they hate her are like family to her. She considers them as her brothers. They went so far to lay down their lives for her then.

I don't get why would they attack her like that in the earlier episodes of the anime during one of the exorcist exams. Izumo was with her friend in the girl's bathroom where they were attacked and on summoning the spirits, they turned on her. It makes no sense.
Familiars in the manga are actually tamed demons. If the user is not properly trained in controlling them or have a disturbed state of mind then the go out of control. Before Izumo was attacked by ghouls, Paku said she was going to quit the course. Hence she was in a disturbed state of mind. So the familiars attacked her.
According to wiki about her foxes


  White Foxes appear to be very proud, even willing to turn against those they've been raised with if they sense weakness.