Goody Two Shoes
You have morals and you make them known. You probably look down on your sisters who party a lot or do other scandalous things. You might even be kind of pretentious about it and/or a narc. For fun, you probably bust liquor stores that sell alcohol to minors.
More true when I was in college than now. Everyone's grown now, we don't live in close quarters anymore, and we are more considered with our own lives. I still bust liquor stores that sell alcohol to minors. Less pretentious than I used to be but it depends on the topic.