User blog comment:B214/Gray power up analysis/@comment-24546844-20141214133817/@comment-7418318-20141214144402

Fairy Giltter and Urano Metria were temporary (Lucy had to learn it by herself after the initial use granted by Hibiki) so you can't just equate those with Ice Devil Slayer Magic.

About Aquarius' power I don't want to speculate just yet, since we don't know if it's permanent or if it even was Lucy to begin with who cast the shield. Since she was surprised about there being a shield, it's quite possible that the CSK allowed Aquarius to cast magic through Lucy, rather than Lucy being the one to use the shield.