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You can weaken the boss by finding some items called hiragumo fragments scattered through out the stage. I did not encounter and trouble with leg armor at all; prob because I was looking for extras and items. She crawls slowly, you can get her with ranged items, guardian spirits or bombs. Keep going to her side as you dodge. You may find yourself in a good spot, like her rear, where you can flank her. Her counter to flanking is predictable. She will do a spin attack. Back up, after a few hits. Let the spin pass, come in again for a few hits. You are lucky if she spins yet again, as you can do the same thing.
Let me add that to flank her, you don't just dodge to her side. You should move around her,while looking for an opening.
hitting the boss in her rear where the amrita is concentrated (also applied for other bosses) gives a little amount of amrita. I have tested her amrita and gold drop by fighting her without any equipment that will increase amrita or gold earned from the boss. amrita earned : 12852 ( might be less because I hit her in rear as final hit) Gold earned : 1254 This is just a guessing, may be the amrita and gold earned increase or decrease depends on how many times you encounter the boss, I will test it again tomorrow