No one knows whether a god exists. If it exists, no one knows the nature of it. No one knows if a god wants something from humans. What we call religious beliefs are simply opinions, of no greater value or merit than opinions on any topic. There is no reason to privilege opinions about an unknowable topic, of all things.

The framers wanted freedom of religion precisely because history taught them how monstrously cruel one religion's adherents can treat other religions' adherents and nonbelievers. Burning people alive comes to mind.

If the website creator is in the stated business of creating Christianity-oriented wedding websites, that's fine. It's akin to a Christian bookstore. But as a public accommodation she should sell the websites to anyone who wants one. Can a Christian bookstore put up a sign saying "no gay people"?