You could also give her the Fourth Bracelet. This has 78 defence, 100 magic defence, and 3% on both defence% and magic defence%. It has a link thing that looks like this O=O O=O O, and it adds 20 to the wearer's Magic stat. Although it has one less materia slot than the Mystile and the Minerva Band it has the best magic defense in the game, as well as the added 20 points to her magic stat.