From "The Transgendered World of the Chevalier/Chevaliere d'Eon", in The Journal of Modern History Sep. 1995, p. 585:
"Finally, between 1777 and 1780 (i.e. after d'Eon crossed the gender boundary), he went through a great spiritual transformation in which he came to accept Jesus Christ as his true Lord and savior."
A good biography is Monsieur D'Eon is a Woman , by Gary Kates. Part V of five is titled "D'Eon's Christian Feminism."