Given how rare it is in sydney for a different price to be charged, I think it's likely the lady didn't realise she was getting a cheaper rate. I always get a takeaway cup because I prefer the taste!
Yes, once told, she had to leave, but I still think it was fine of her to make the point that kicking her out of an empty area seemed a bit mean. Sure it was policy but she wasn't deliberately flouting it. So I think her initial comment was fine - she gave feedback on her treatment as a customer and their policies. Their response to her was appallingly, disgustingly rude. Hacked or not, that is sure damaging to a business!