User blog comment:Derax-Pagani/Chapter 507: Voice/@comment-7418318-20161024153946/@comment-7418318-20161025145659

I highly doubt a mother/creator would tell the daughter/creation "I am you and you are me." unless they were created out of parts of the mother/creator.

"I cut out one of my kidneys and made it into you" doesn't sound very likely, though I guess the scar would be more or less in the correct spot, except for being on the front instead of the back. But we all know how reliable Mashima's knowledge of anatomy is. ^^