Ryujin
Legend
Religious motivation is not sufficient for invocation of the Establishment clause. It could even be argued to even be unnecessary, but I can't see a situation where a religious test occurs without religious motivation without doing some very unrealistic logical limbo dancing.
If having religious motivation for doing something is sufficient, get ready for Establishment clause challenges to such things as Medicare.
I get that people would really like to see the use of the 1st via the Establishment clause used to show that this person's use of the 1st is invalid because it would be a fantastically ironic twist, but it's not a case you can win on.
cf. "Endorsement Test" and related decisions.
... or we just skip the First and jump right on down to the Fourteenth Amendment, like the USSC did.
... or somehow get her to run afoul of the IRS. Those buggers just don't give up.