she got arrested because she broke the law. im not fully sure on american law however i know recently america finally got marriage equality, if you dont agree with this then its fine but whats not fine is denying a 'government' service that is open to everyone because you have the 'power' to do so.
she wasnt arrested for being christian, she was arrested for using Christianity as an excuse to deny service to someone and generally be a tosser.

to say shes a strict christian shes had about 3 husbands which im not really caught up on this but im guessing this is also frowned upon