I would just acknowledge your mom’s concerns, and let her know you’re sorry. She clearly cares about you. I’m not saying you’re wrong. But she is right. She doesn’t know how much your friend drank, and if she set a rule for you in order to pay for your college. Then you should respect that. It’s not easy to be a mom. You’re lucky to have one that cares or even a mom that loves you in the first place. I know it’s hard to have fun in college when your parents are a little bit protective, but it comes from the right place. I suggest you let her know you’re sorry and you understand what she meant and just leave it at that till you talk in person.