User blog comment:IamJakuhoRaikoben/Chapter 492: Elder Sister and Younger Sister, Review./@comment-1359322-20160704160505/@comment-7418318-20160704161259

Now that you mention it... I didn't even consider it before but it is indeed a bit weird that last chap Irene did that giant eye thing only to ignore Erza and go after Mira instead.

Maybe it is just a thought projection near Mira to deliver a threat or have a conversation or something... or she saw that Erza wasn't who she thought after all and thus lost interest. ^^