What is the drinking age in Nebraska?

I ask this question because I was at a Pizza Hut in Nebraska and I was meeting up with some older cousins and Uncles and Aunts, etc. And they stayed open late cause we was a big group and my older cousin shes about 19 years old and she was drinking beer/margaritas and the pizza hut people were giving her them (maybe cause they were in high school or fairly young) Is the age lowered in Nebraska Pizza Huts? Or did they think my older cousin (girl) thought was older then 21?