I have said it before and I will say it again...I think privately-owned companies (assuming this is one) should be able to hire and fire anyone for any reason...
...going bra-less, the color of their hair, skin, nails, shoes, their sexual preference, because they won't sleep with the boss, because they will sleep with the boss, the way they part their hair...ANY REASON.
I don't care what the law says about this...the power of consumer choice should be the final court.
If this gal stays fired, she can tell the press and customers can boycott the business (or not). And that will force the owners to do the right thing (if that is the case).
I have zero problem with her being fired.
I hope she loses her case...but she probably won't.