User blog comment:Miskos3/Fairy Tail Chapter 385: The Celestial King vs. the Underworld King, Review/@comment-5268982-20140523091106/@comment-7418318-20140523094510

If she keeps those powers, I hope she'll start out with barely managing to do anything with them in the beginning and having to learn and train to use them, rather than having full control and perfect skill with them.

In emergencies like this one, she could always have instinctive flashes of insight or something that save her, much like Natsu had throughout the entire series (the most obvious being the way he managed to eat Zancrows black flames).

Or maybe now that Lucy is fused with part of her powers, Aquarius can channel some of her powers through Lucy without leaving the Celeastial Spirit Realm. That would explain how that water-shield went up without Lucy even knowing about this power-infusion yet.