Ohhhh, I get it. She can see different wavelengths of light. This is based off of those stories about people testing out IR cameras in the vietnam jungles being able to see demons.
This is why I like Korean manhuas. If this was Japanese, she would have been ostracized for being a "monster," with everyone shitting on her. This girl actually asked for it, experienced what MC experiences herself, and didn't berate her for it.