User blog comment:Miskos3/Fairy Tail Episode 238: Tartaros arc: Immorality and Sinners, Review/@comment-24039234-20150620103048/@comment-68.179.188.168-20150620111020

Or in even easier answer Mashima retconned XD or she has to be in her "demon" form to be able to negate it, Mira's pretty weak in base form