Willow Rosenberg is a pretty skilled magician, but she will have to essentially deal with multiple skilled opponents at once since Lucy can summon her Zodiac fighters to help her. Whether she calls in Leo or the Water fighter, it would be too much for Willow. Spells are only as good as the mage who is summoning them and Willow is a bit of a glass cannon. She can dish out the damage, but she definitely can’t take it. Lucy Heartfilia wins.