What is my best play? (with some NSFW)

[benza13]

I have a situation with a female. I am home for the holidays and went to the bar tonight where I saw many old friends. One of these old friends brought his little sister who is now 21 (I am 23, so its not that bad). She admitted that she had a crush on me in high school and we danced most of the night, and ended up making out for a while at the end of the night. Her older brother is a friend of mine, not one of my best friends, but still someone I hung out with quite a bit. At the beginning of the night he tried to tell me that this wouldn't last more than a few minutes. By the end of the night he was telling me to go for it. Obviously since I am only home for the week I have to ignore the 3-7 days before calling. So, should I be calling her tomorrow night to try and close the deal, or should I respect an old friend and not bang his sister then head back home? And no, I don't have any pictures of her, but I would rate her at least an 8, possibly higher but my judgment is clouded as a friend of her older brother. I know that if I pursue this I can definitely close the deal while I am home, but am having trouble with my conscience. Thanks OOT, here's some repayment for your valuable advice.