My sister is 21 years old I am her older sister.?

She just turned 21 yesterday and went out for a couple hours with friends to have a few drinks. She has a car and it's in my name and the car insurance is under my name too she in named as the driver for her car any way I don't want her drinking and driving am I right? So I dropped her off where she met her friends for drinks and then picked her up last night. Now she is talking about going out Again with other friends for drinks. I told her again she is not taking her car (actually my car). I told her just because she is 21 does not mean she has to drink alchlisum runs in our family so I do worry about her. She said I am being a prude am I right to feel the way I do and is she right am I I prude.?