Father Burke: The blood of Jesus Christ.
Frenchie: Holy shit!
Father Burke: The holiest.
Sister Oana: Whatever you do, don't stop praying.
The Nun: The village will lose its idiot.
Father Burke: Next time do use the shotgun.
Frenchie: What's the opposite of a miracle, Father?
Father Burke: I'm afraid there is something very wrong with this place.
Answer: The nun was trying to find the relic. The deceased nuns had no actual idea where it was. That's the whole reason Irene was summoned by the Vatican because she had visions about "Mary pointing the way" also the "ghost nuns" more than likely have something to do with her clairvoyance as well.