Very sad story. It sounds as if the parents were trying hard to nurture their child in what they misguidedly believed to be the best possible manner.
Exclusive breastfeeding is natural at a year old, albeit unusual in our society. That in itself should not have caused a problem for a healthy, well nourished mother and child.
The need to ensure enough Vit B12 in the diet is well known amongst vegetarians and vegans - B12 deficiency can be very serious for an adult, let alone a nursing mother and baby. Maybe this sorry story will alert other well meaning parents adopting strict diets, that extra care is needed.
Whatever our views on meat/factoryfarming etc etc we simply have to recognise the fact of nature : human beings are omnivores and it is entirely natural for people to eat meat.
(I'm vegetarian btw)
www.bupa.co.uk/health-information/directory/v/anaemia-b12