Trust me, the Chinese broad was naïve — and dumb. I know many local Chinese youth who know very little of the cultural practices of the other ethnic groups – thanks to the segregationist policies of the PAP govt. Many think that if the food doesn't contain pork, it's halal. Most of the SAP school alumni I know did not have a single minority friend throughout their school years.
And yes, the vitriol hurled at the Malays/Muslims in this thread is unwarranted.
That said, I didn't find the restaurant's reply particularly offensive: "This is Singapore, not Saudi Arabia." Not a rude reply by any stretch, nor an attack on Muslims, but a sarcastic reminder to what they felt was a stupid question posed by a Chinese that this being Singapore, you wouldn't imagine a pub to be certified halal in the first place.
I'm very sure had the questioner been a Malay, the restaurant would have replied in a more neutral manner.