User blog comment:Miskos3/Fairy Tail Chapter 490: Fairy Tail Zerø, Review/@comment-5268982-20160622085020/@comment-7418318-20160622085616

The way I understand it, she cast the spell specifically to move Zeref and Acnologia and didn't care about anyone else and thus left their position up to chance. Seen that way it's hardly surprising that she wouldn't know where others end up. That she cast the spell the first time and cast it on Acnologia (who might have done something to attempt to resist) further complicates matters, creating more instability and thus unpredictability.