I'm going to prank my naive kid sister, who just got her first bottle of perfume. I'm going to tell her to use at least half the bottle at a time.
She looks up to you for guidance. That's a cruel, mean thing to do.
I think it would be hilarious!
It's wrong to try to make your little sister look foolish when she's looking up to you for guidance. You should emphasise how strong perfume is and that she should use only a few spurts. Telling her it's okay to use half the bottle is not only a waste, but will make her feel humiliated when people react to the overpowering bouquet.
Maybe that'll make her stop pestering me.
Being an older sibling she looks up to, you have a opportunity to offer her your invaluable life experience. Giving her bad advice just so you can laugh at her is mean. Think about it -- how you'd feel if the roles were reversed?