The thing is, most women who are breast feeding tend to know that after three months, the babies start to feed on a schedule - mostly they get fed every four to six hours. So, If a woman wants a cupcake, make sure the baby is fed right before you go out for a few hours on the town. That's what my wife and I do - we may pack a bottle when we know we will be gone for more than four hours, but we always time our outings when we know that my daughter doesn't want food.
If this baby was a newborn, the mother shouldn't be out eating cupcakes at a bistro anyways. Or, have someone bring her a cupcake - or go for a quick outing after the baby has eaten. There are PLENTY of ways to cope with feeding schedules. When you have a kid, it's no longer your time - it's their time.
ALSO, I don't know how many of you have heard of an aspirator... But the mother that wanted to go for an outing could have pumped beforehand while she was at the house and if the baby was hungry, then pull out the bottle of breast milk.
Flower, you said there's a problem when it comes to mothers who have large breasts who feed their kids - my wife had the same problem and I am familiar with that situation, however, even when covering the baby up, you can still feel yourself and the babies nose and make sure their airways are clear.
I'm just offering up options that she could have done besides whip her tit out in public, not saying that I agree that it is rude, or agree that it's a completely natural thing that should be overlooked.
From a male perspective, it can not be overlooked. From a female perspective, of course it can.