Because she casted a legendary spell known as "Universe One", which shifted the geography of the entire country of Fiore to her whim; her magic not only allowed her to shift numerous buildings like Mercurius and Kardia Cathedral next to each other, she also shifted Zeref straight to the Fairy Tail Guild Building with all of its' members completely empty (aside from Mavis), and brought Gajeel from the Underworld straight to Tenrou Island with a revived Zera. This proves that she has Large Country level Hax Attack Potency, if you look on her profile on VS Battles Wiki

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