Extended Breastfeeding at what age does it stop being appropriate?

When I saw this article in my Google news feed I was immediately grossed out. Don't get me wrong breastfeeding is amazing and I definitely will try to do it when I have babies. But when does breastfeeding cross the line from feeding to uncomfortable and unnecessary? How does anyone know for sure that this girl really wants this or if she's afraid to tell her mom no? Does anyone else think at a certain point if you live where food is readily available and extended bf is not necessary for the child's survival that it might be crossing the line into predatory behavior? She states that she does this to bond with her child, but at this age is this a healthy way to bond? What are your thoughts?