The store has their right to set their policies.
She wasn’t really doing anything wrong, just against the store policy.
I’ve never understood why people aren’t clear on the concept of “legal tender.” If I am a storeowner, I can refuse your payment of a $100 bill for a pack of gum.
Yes, they do. Of course refusing to accept legal tender will get you into all sorts of issues a business doesn't want to be in.
Bottom Line the Store was dumb. They got a snoot full of bad publicity for no good reason.