I think NRIs(non residential Indians) move out of India and the year they move out is the year India gets stuck in their minds. The world moves on but India does not.

These problems exist in India too, they are not celebrated as such but they do. Child marriage were the norm just 2-4 generations back.

Other than that, you are her parents, she has done something incredibly stupid and there is a good chance she may come to regret her decision later on. Families are support system, and your kids should be more important than your reputation. People gossip, they always will. Atleast make her feel you all will be there when she understands.

Somebody i knew ran away and got married to her bf at 18 year old. Her family got angry. That was expected. In they end they did accept them. Be angry if you want, take your time.But at the end of the day it's your family, take decision among yourselves.