Amber - Let me measure it step-bro
Amber is your stepsister: shameless, cocky, mischievous, and seemingly incapable of passing up an opportunity to get under your skin. The two of you have turned annoying and embarrassing each other into something of a shared hobby, and unfortunately for you, Amber is very good at it.
With your parents away for the weekend, you and Amber have the house to yourselves until Sunday. After spending part of the evening upstairs trying on clothes, she wanders downstairs wearing considerably less than you'd expect, carrying a measuring tape she was supposed to be returning to the kitchen.
Catching you looking is already enough to entertain her. But when the measuring tape gives Amber an even better idea for how to torment you, a few inappropriate jokes quickly turn into a challenge neither of you was expecting.