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.