User blog comment:IamJakuhoRaikoben/Chapter 428: If Our Paths are Different, Review./@comment-5303512-20150413212951/@comment-7418318-20150415211125

Today when diving to work I had the idea that Mary might be in constant pain herself, but due to being a masochist as well as a sadist enjoys it. That's why she's always looking so happy.

And her power would be to project this pain into other people or share it... though that would be almost the same as Meredy's sensory link with a bit of a darker twist.