Well she's sentient. I suppose that much is fine. Koishi's abilities are passive but are most effective on biological creatures and work even better on things that are self-aware. If her thinking and perception are dictated by her electronics then Koishi's abilities wont work as well.

Keep in min that this is neither good nor bad. But if koishi finds out that her passive "invisibility" doesn't work very well on 18 she will never leave 18 alone. She likes being noticed. x3