julez, my thoughts are with you! When I was at 13 days (I am at 7 years now) I could not go to any party where alcohol was being served.
"Its my own business, my own problem, and I will do what I have to do for my sobriety."
Okay its your sister so you obviously feel obligated. How about this as a plan: After the first hour or bar say you are not feeling well, call a cab and head home?
Dave