I don't think MC specifically designed the equipment to do that, but rather just the effects of her using her full mana-power.
Mana in this world can have elemental aspect tight to it (fire mana, light mana, even death mana), so I suppose Girly's mana is a wind type (at the very least).
The equipment was made to absorb mana, but before it wasn't absorbing enough to awoke any elemental effects. Now, not only there's enough for that, there is so much that (I believe that) the mana itself is morphing the equipment to be more fitting with the fight-style.