I know I am late to this, sorry in advance.
I guess you mean the fight in Midnight Church.
I have the same problem.
After I reached the bad ending, every attempt at fighting her ended up in no post-battle cutscene.
You gain control over your character, you can pass through Olivia but not interact with her or anything else.
And if you are going back the way you came, you step over the event tile which triggers the battle again ending up in a softlock if you have 0 HP.
The check for the switches controlling which ending you get gets skipped for some reason.
I couldn't figure it out, and in case someone has the same problem, I have come up with an ugly bandaid solution.
I edited the affected map to feature a literal switch that repeats the check for whatever ending you were going for.
It will be right next to you when you can move, so you won't miss it
Just replace the original "Map311.rxdata"-file with the attached one in the "Data"-folder before you start the game.