User blog comment:TheCarrotSaysYumYum/Fairy Tail Chapter 416 (Tartarus Arc - Last Chapter) Review/@comment-4449950-20150119140128/@comment-63.135.255.62-20150119145019

Maybe Mirajane absorbed the demon particles inside Minerva's body. After all she said she used them for her demon take over and since Minerva is on friendly terms with Erza, it wouldn't be strange for her to ask Mira for a favor on Minerva's behalf.