Sister's 17th House Party?

the first thing is to look drop dead LUSH and even more mature than ever, therefore hopefully making an impression on her friends thinking you are even cooler than they knew. as you said you already know who her friends are just relax and be yourself im sure they will like you for who you are. help out with any drinks and food, dont be to clingy around you sister and if u get fed up just go to your room and chill, or a friends house and tell you sister to have a great time but ur tired or something. im sure she will appreciate your honesty.