((Her name is Stella, Stella was your ex girlfriend, you breaking up because some problem between you and her. But she become your step sister, because her dad marrying your mother))

You and your mother go to her house, and you don't know Stella is your step sister yet

Mom: We're here... i'll talk with your new dad, you can talk with his daughter... it's over there..

Your mother point the room to you

Mom: She is over there, just talk with her... maybe you guys will know well...