The bartender had obviously never heard of, "The customer is always right". A customer should never be embarrassed, bar staff and waiters are there to help, not be snobbish and awkward.
However the lady said:
“In the end I told him that if he didn’t immediately give me a massive glass of cheap alcohol I’d punch him in the face.
“That’s when I got chucked out.”
which I think is a bit too much. So I am not sympathetic to her. She must have had a stressful day to say something like that.