Aren't Bostonians kinda ornery? Maybe this isn't such a huge faux pas locally, or it's been accepted as her shtick. What Bostonian doesn't like sticking it to a New Yawker?

The restaurant's rating in Google is 4.5, so it can't be that bad (I didn't check Yelp). In the Boston .com article she claims they are very busy, so the bad press hasn't hurt them yet.
More generally, there was a time when business policy was "the customer is always right." In 2024, that isn't universally accepted anymore and this owner relishes antagonizing her critics. Like you, I'd never support a business like that but apparently others are more flexible.