The Nun II producer James Wan has opened up about how returning characters Sister Irene (Taissa Farmiga) and Frenchie (Jonas Bloquet) reunite in the sequel film. The end of 2018's The Nun teased that Frenchie had been possessed by Valak, The Conjuring Universe's major demon antagonist. The Nun II picks up four years after the first film, where Irene must once again face the demon as it resides in Frenchie.
https://screenrant.com/the-nun-2-story-details-sister-irene-frenchie/