Quote Originally Posted by Buffalobiian
I'm trying to find a relationship between either her emotions or her thoughts and the eye activating. As the miko said, her hair only becomes that after "something" happens, and I gather it's shock, which also resulted in her eye.

My initial thoughts are that it's probably got to do with how she "seald her heart", and maybe when that eye opens, it's revealing that she's temporarily opened it up or something.
In the first episode, her eye changed before her hair did. She blinked and it changed to the cross, it changed back when she realized her father was killed (it was normal when his head separating from his body was reflected in her eye). Then she screamed and her hair turned white. I do think it is a similar effect to what you said. It changes when she says something more significant, often relating to her quest and the power she hopes to achieve from it. We see it in the first episode when she says that, "I can already see it. It is within my grasp!"

In a way, she saw Shichika's father with the same eye she sees Shichika's power with. Perhaps she saw the power that was used to slay her father could be used to give her back the position she lost. I'd have to go back and try to see if there is a common vein with each of the scenes to be sure.