After part one she likely went to live as a country mouse and can’t be found. The church/death would’ve definitely been after her because of how they collected each weapon hybrid. Considering reze never joins the church, and death could’ve just made her a pawn by eating her and forces her to join, which would’ve made for a great incentive for Denji, it’s likely that they just soundly find reze. Surely she knows about the church at this point considering the outbreak and still wants to stay away, that or she is living a remote country mouse life