Pumping breast milk

I have a friend who no longer breastfeeds but she still pumps for her son. Age 4. She gives him breast milk in his cereal, to drink during lunch, etc. so many people attack her and say that's gross or not natural and blah blah blah. But she plans to keep doing it literally until he's grown. She doesn't believe humans are meant to have cow's milk or any other kind of milk for that matter. What are you guys' thoughts?