I think it's odd and it's more about kids seeing it. Does a 6 year old need to see a woman's bare breast? Breastfeed all you want, but put a small blanket. You don't even have to cover the baby just enough where the breast isn't exposed.
6 year olds SHOULD see a breast used for what it's true function is. Breasts are biologically made to feed babies.
She could so easily pump her own milk and give it in a bottle when she's out in public like that. No need to let it all hang out for the world to see.
Clearly you have not had an infant that won't take milk from a bottle. Many breastfed babies don't take too bottles very easily, plus it is MUCH more convenient to nurse a baby than to take an extra 30-45 minutes to pump the milk from your breasts, put it in a bottle and warm it up to feed the baby. It makes no sense to do it that way.