Ex-cult member here.

The only thing that snaps someone out of that spiral is an internal realization. There’s nothing we as outsiders can really do directly. Engaging with their version of reality (Christian evangelicals specifically) feeds into the prosecution complex and perpetual victimhood that validates their position. It’s a self-defeating tactic to confront them directly.

Focus on positive, normal, consistent interactions. Share your regular, everyday triumphs. If your lifestyle comes up in conversation, express being satisfied with it. Decline going to church with them. Don’t debate their stances on doctrine if you share a root faith. Deflect and redirect. When the opportunity arises, maybe ask a question that invites some introspection about the subtle (but structurally loadbearing) flaws in their worldview. But don’t probe too much. Again, bear in mind, they’re trained to take every perceived attack as a trigger to rehearse their dogma. Be subtle.

And above all, unless they are actively abusing you, don’t abandon them. That’ll seal them in and you’ll never get them back. Continue your hobbies and appointments, and keep a schedule (movie night, for example.) Eventually, they might feel vulnerable enough to express their insecurities about inconsistencies in their worldview. Be gentle with them, as this is a remarkably scary thing for them to even voice out loud.

If they love you–and I mean really love you–no preacher with an ego to preen will ever take them from you.