User blog comment:IamJakuhoRaikoben/Chapter 474: In the Moment of Complete Silence, Review./@comment-27792306-20160222233857/@comment-9595671-20160223000137

It's possible, plus if I remember right I think certain magic attacks bypass her water body. Even though Juvia could just take an attack, she can't always know if a certain spell will be one that does bypass her water body and harm her.

In fact, maybe there was some lasting effect from the poisoning she received after she burst out of Keyes's body like we saw with Laxus in the last few chapters, though for her it affected her water body.