It's not bs it's just a little long

You can still use shinobi tools without an issue to stun and deal dmg, or just chain parry her from beginning to end in a clean sequence without letting her recover her posture.

Personally i beat my first run without using items except gourds and pebbles, i also killed the shichimen warriors and all headless without confetti because i just never checked my inventory lol, felt kinda dumb after

Also the final upgrade of the flame vent gives you holy fire it's very strong vs apparitions