Ask her which christian god she identifies with and ask her if she'd apologize to the other christian gods for picking the wrong one. Then she can move on to the other abrahamic religions with related but different gods that are apparently worth killing each other over. Then it is time to do a polite check in with the other non-abrahamic world religion gods and pay her respects because I mean what if. And after that it is worth mentioning that the abandoned religions that were the precursors to all variants of christianity might actually be the right one, unless she is prepared to admit that the current one she believes in might also be wrong because it is actually a future evolution that finally got it right...
Of course this is just a smug elaboration to point out the absurdity of the situation.
Personally I'd probably just quietly drop them from my social circle.