User blog comment:IamJakuhoRaikoben/Sorcerer Magazine, Issue 41: May 2015/@comment-1153699-20150602132933/@comment-5268982-20150602210450

Also since you decided to use images: The ones you chose had Minerva taken by surprise. Something that has happened to literally every character in the series when plot demands it. Mira was taken by surprise by Elfman and Evergreen but I doubt that makes her slower or weaker than them.

here you see Erza actually commenting that Kagura is moving very fast even for her, and still Minerva switches them around with no sweat.

and here in her debut, she blocks Natsu's LDF(with Laxus' thunder, mind you) again without sweat.

I guess this settles both arguments about her reflexes and her durability.