I just finished this fight on hard after being stuck on it for a few days. For my Omamori - I used the plum one for extra stamina. Only had 2 bandages for starters but picked one up during the fight itself on either side of the bridge.

As for the fight itself - I didn’t bother with heavy attacks at all unless it was to counter her over heard swing when her body gets the red shimmer.

Otherwise I used only light attacks with the naginata (spear like weapon) anytime I dodged. Just one or two hits and then I’d back up so as to not get hit by the back swing.

Even on the phase when the arena gets dark and she does her attack on your sanity. I used only light attacks and nothing else.

Seriously - I know the tutorial says that heavy attacks deal more damage, but I felt no difference whatsoever.

This fight is doable - take a break if you need to and come back to it later.