>>2175102In the church you should first exhaust the dialog options with the priest. Then try talking to the blue-haired girl who follows you around. This should allow you to interact with the bookcase door. Then you just need to talk to the priest again to be able to challenge her.
Note: After this you will need to interact with the girl from the previous area to clear the next area. i.e. You have to talk to the priest again to challenge the girl after her.
