It is the Duty of the airline company to check all required documents .Lufthansa should have checked if they were carrying a valid India Visa just because of their mistake the family had to suffer .I feel bad for the lady and her daughter but When it comes to immigration they have to be strict .Trust me if an indian passport holder had gone to the U.S without a valid visa they would have first grilled him with questions for hours and then they would have deported him .I think the famil should sue lufthansa as the carrier is suppsoed to check the documents (if they did not do an online checkin in that case they accept that they have all the required documents).