I think it is terribly sad, tragic but there's a bit too much vitriol here for my liking.
The mother is proud of her daughter for keeping the child, not necessarily for getting pregnant. In any case what else is she supposed to say - my daughter is a slut? Of course she is going to put a brave face on it.
Secondly I know a lovely family whose daughter went wild, completely out of control, at 13, the other children were perfectly well behaved. If their parenting was at fault is it hard to see where. We aren't in a position to judge the mother on so little information.
Physically and physiologically an 11 year old is far too young to be pregnant, there are dangers. But psychologically she might be better at parenting than a 16 year old who will probably have become more self-centred by then.
I feel sorry for the 15 year old boy. Young teenage girls gravitate towards boys a few years older, they always have, always will and often look older than their years. Having sex with a 11 year old makes him a criminal, if she had been 16 he would have been the victim. Where is the sense in that?