When a guy ejaculates in a girl, sending his holy ghosts to haunt her sacred place.
After a girls had sex, her "church" is likely to be "haunted" for a short time after and it's not advised for anyone else to go poking around unless they are super brave.
Haunting the Church:
Bro 1: "Hailey just gave me the eye, I think we're going to go back to mine for some 2 person push-ups."
Bro 2: "Easy there Bill Murray, she was doing some gland-to-gland combat with her ex at pre drinks. That church is haunted for sure."
Bro 1: "Sounds like mass will be in the Rectory tonight."
Bro 2: "Spooky..."