Here "she" refers to the people of God. John speaks of the righteous acts of God's people as if they were a bright and clean dress that a bride wears on her wedding day. You can state this in active form. Alternate translation: "God allowed her to wear a dress of bright and clean fine linen" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-activepassive]])