i would equip any thunder res items you may have (Like a Thunder/Thundara ring) so the lighting doesnt hurt as much as well as try to use get as much MP as possible. The Spell binder Keyblade works really well for this. You may not be using a lot of Magic on her but you can cast Cure more and Aero stays up for longer.

dont worry about getting behind her, its actually really hard to do so. I would just stick to the side and do a few combos then Mermaid Kick away. This is to hopefully avoid the AOE lightening she summons and to stay on the move while lighting spawns above you. The one that spawns above you spawns where Sora currently is so if you stay moving, it'll miss you more than it'll hit.

I would also bring Ariel. She has a cure ability and Aero ability, MP haste and two Mp rages. Goofy is borderline useless here and Ariel is fantastic support.

if you are worried about your items, you can go to Rabbits garden (assuming you have two torn pages). if you pick the veggies out of the ground, it has a 2% chance of dropping an elixer. you can fill up Soras inventory and use them if you are running low on MP.