User blog comment:FairyRaven/Fairy Tail Chapter 456: Orders, Review and Commentary/@comment-24039234-20151010122633/@comment-173.66.81.211-20151010200322

I take it you forgot how the fight ended? With Mira taking over a part of Seilah's power and using it to use macro to summon Elfman? It's quite apparent from that, that "Mira can't take over Seilah" wasn't a matter of "Etherious can't be taken over", but rather "Mirajane isn't strong enough to take over Seilah". Which is something that would obviously change when Seilah's dying and Mira's regaining her strength.