Hi - your question is an excellent one. In the 1970's or there about the drinking age was raised to 21 by most if not all states. This was the result of the increasing number of deaths as the result of drinking and an attempt to reduce that number. There is no link between those laws and the laws that govern the age of majority and the laws that govern the right to give consent to sexual relations. They are all over the lot, particularly in the South. Some of this is based on biology - we know that the frontal lobe of adolescents does not fully mature until the late teenage years and some of it is based on the educational system - most people are 18 by the time they graduate from high school. Unfortunately, there really isn't any way to apply logic to all this - there are too many conflicting agendas that come into play in setting age limits. The control that the parents of this college girl did have was to take her out of school by stopping her tuition - after the age of 18 the only control parents have is financial.
Just my opinion and thoughts.
Thank you. I wasn't sure. In my country the legal drinking age, the age that you can marry w/o parental consent and the age of majority is the same - 18.