Is it normal that i went this far to protect my sister?

I'm a 20F college student. When I was 16 (and my sister was 18) we both went to a party where somebody brought alcohol and we both got tipsy. She thought she was good to drive by the end of the night, so we didn't think about calling anyone. We should have. We were almost in the clear, but she missed our driveway and instead turned her car into the drainage ditch in front of our house. The front got banged up pretty good. Luckily, our parents weren't home to see it. A neighbor did though and called the police. Before they arrived though, I talked my sister into letting me take the fall for her. I pointed out that this could totally mess up her plans to attend college out-of-state. Plus, she'd have an adult record. She agreed to the switch.

I ended up spending a week of my summer vacation in juvenile hall. Plus, I was on probation afterward with lots of community service to perform. Mom and dad were mad, of course. They eventually got over it and to date neither of us have ever told them the truth about that night.

I recently confided to a close friend what really happened. She seemed to think I was nuts for doing what I did. I know most people wouldn't be willing to go through all that to protect a sibling, but is it really that crazy? She definitely learned her lesson without the legal trouble. I was able to have my record sealed at 18, so it's never really affected my life. The two of us, who were always close, were even closer afterward. I've always thought it was for the best that I got the charge. What do you think?