[Boogieman]

“She states that the ATF told her (when she received her FFL) that if she feels that a customer is a threat to the safety of her workplace, she can refuse service.”

There’s a huge difference between “a customer” (an individual), and an entire class of customers whose only common characteristic is their religion.

[RandallFlagg]

Yeah, I know.
Which makes the bacon idea sound better.

[Dead Corpse]

"There’s a huge difference between “a customer” (an individual), and an entire class of customers whose only common characteristic is their religion propensity to cut peoples heads off."

Fixed it for you.

She is well within her Rights.