Helpful Tips for Normal/Hard Mode:
-It's possible to avoid getting slashed by Saiko in her "happy mode" as you gain progress by not looking at her (at least for too long).
-Likewise, it's also possible to avoid getting your keys stolen while keeping her "happy" by not looking at her and pressing the sprint button in short spurts, which will give a small distance between you and her.
-Let her choke you out and lock you in a room, as this gives some time to check rooms without worry of being attacked.