well, I can completely understand the mum with the adoptive girl. Breastfeeding a toddler is lovely for cuddling and bonding, and to me it makes sense to want to do this with an adopted child.
The one feeding twins - she should have cut down gradually, it's not all that hard. I breastfeed ds (2.25) before he goes to bed. Dd1 was breastfed until 3.5 and self-weaned. I didn't feed them on demand when they got a bit older in the same way that I don't give in to every other toddler demand.
Now - as to woman breastfeeding the 8 year old - mad as a box of frogs.