9. On a double date, she’s always your wingman.
It might cost you though. You may have to give up that killer pair of heels or the cute little sundress that she really likes if her date is a loser. It’s worth it to have her by your side.

10. You can tease her mercilessly—just not in public.
When it comes to the sister relationship, in public you always have a united front. In private, any subject is fair game no matter how sensitive. Just be warned, she’ll do the same to you.