The post game version? Spellweaver there has to be handled similarly to how you handle Lingering Will's desperation attack in IIFM.
After she transitions into spellweaver, she'll fire off projectiles three times in a row. Cartwheel past them. She'll teleport elsewhere after, but listen for her laugh. Once the laugh ends, immediately block. She'll teleport twice within your frame of view and then attack from the other side. Block again. She'll teleport in front of you quickly, then attack. Block once more, then use doubleflight to avoid the projectile. At the height of your second jump, guard again, as she'll attack you twice in the air. When she hits the barrier twice, Air Slide forward to completely avoid the projectile barrage. When she's winding up for the Spellweaver finisher, wait for them to start closing in on you and guard, but this time, use the counter (you need the i-frames more than anything). While the counter animation is protecting you, you can hit lock on, and Aqua will lock onto to the real phantom Aqua, and you can attack her as soon as she comes out of the finisher.
About 99% of the time after the Spellweaver bit, she'll cast a nasty Ice spell with insane tracking. If you lock on to her and cast Thunder quick enough, you'll knock her right out of the attack.
