I just thought. Koishi state was caused by her clothing her eye and thus severing tie to her counscious mind. As such she only act upon her subcoscousness and inner desires of her heart. Only recently did she show any semblances of self-awarenes that were caused by her sort of "opening up" to Sanae and co. So. Mind appears to be aspect more closely related to coinscious. But using light seems like a good idea as well. Less sure about heart tho.

That’s a bit of a philosophical debate right there- You yourself said it, “She only acts upon the inner desires of her Heart, her subconscious, wouldn’t you say one erasing ties with the Conscious Mind would be more tied to Heart in turn? I was also thinking about the nature of the power rather than the effect- If you go for Mind, yeah like, vanishing from their Minds as soon as they’re done acknowledging her. But that also feels somewhat tied to erasure of her presence, of her Self, like it has a stronger tie to Heart.