For this fight, you may want to strike a balance between damage boost and keeping some feathers for healing, because it's a crazy battle.
You can block her long range green weapon attacks -- including the ones where she jumps in the air and swings around -- with your shield rather than wasting the stamina to dodge them.
The green arrows that go up above will just miss you, so don't try to jump or dodge there and save that for when they go lower, at your normal body height.
During the fireballs segment, stay close to Endless and block with your shield, then walk forward and dodge roll.
Multiple weapon types can work out here, but if you have trouble, try switching to a high intelligence build with Unlimited Energy and then spam orb attacks.