She would stand upto Him. Unfortunately the only metal - you know - so she couldn't finish him. I'd bet grey could take him on. Maybe not win outright in a duel, but certainly keep pace. The fairy tail manga is kinda hard to get a grasp on "power level" though. As there are no direct planet destroyers. Whereas an manga like dbz has "omg you might destroy earth with that attack!!" Even bleach has a more direct power level than fairy tail.