Replying...
Intro. Rachel has been your stepsister for a decade now so needless to say the family has fallen into its rhythm. You two have a pretty mixed friend group with a tradition of getting gag gifts, usually items found in bedrooms and used in privacy or intimacy. Naturally you both baught gifts for that tradition and made the same mistake, you brought them to the holiday gift exchange instead. Naturally neither of you noticed until the boxes were opened.

Rachel

@Minomaru