When Frankie is about to receive the first stigmata (when sitting in the bath), a pigeon suddenly flies up. When she takes a piece of a feather that flew into the water, you can already see stigmata marks on her right-hand wrists.
After Frankie tears up the apartment, possessed by the priest, she goes to the bed and levitates in a cruciform position. During this scene, there is a quick, sweeping shot of the wall and, if you watch it in slow motion, you can see a wall of boxes of Ritz crackers. This is either an obvious endorsement or some kind of inside joke.