We have no clue. I know that Jamie Campbell Bower is a Catholic and that Bonnie may be converting( if she wishes) when she marries him. But neither of them seem religious in any way other than Jamie's cross necklace and such. Bonnie doesn't have anything religious that she wears, never had a purity ring or anything to indicate a religion. I think because of her upbringing in an Artists nature environment she is no religious because she was exposed to them all and things like that.