It is a last desperate attempt. The mages with the SDF force will not arrive in time to counter Gamma's spells. Machiko must hope that Gamma is not so powerful a mage that he can know every conceivable spell, that there is some limit to the sheer number of spells he can sustain at any one time. She must hope that the barrier he uses to guard himself against her attempt at manipulation is a creation of the purest mana, useful against spells, against all forms of magic, but not against purely mundane physical objects.